Method for rapidly identifying drought tolerance of sugarcane seed stems in germination period and application of method

Abstract

The invention discloses a method for rapidly identifying drought tolerance in a sugarcane seed stem germination period and application, relates to sugarcane germplasm resource evaluation and drought tolerance breeding, and solves the problem that a sugarcane drought tolerance (resistance) evaluation or identification system in the prior art does not consider the influence of drought stress in the period from sugarcane seed stem planting to seedling emergence on sugarcane varieties. The method comprises the following steps: pretreating upper, middle and lower bud segments of sugarcane seed stems, planting the seed stems in a reserved field, performing drought stress after sowing, monitoring a soil surface state and performing dynamic moisture regulation and control, recovering irrigation after drought stress is finished, and monitoring seedling emergence conditions. Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stem, the drought-enduring grade is evaluated. According to the method, the drought tolerance of the sugarcane seed stem germination period is systematically identified for the first time, and the blank in the prior art of identifying the drought tolerance of the seed stem germination period is filled.

Description

Technical Field

[0001] This invention relates to the field of sugarcane germplasm resource evaluation and drought-resistant breeding technology, and in particular to a method and application for rapid identification of drought resistance during the germination period of sugarcane seed stalks. Background Technology

[0002] Sugarcane (Saccharum spp.) is a core sugar crop in my country, accounting for over 92% of the country's total sugar production. Sugarcane cultivation in my country is mostly distributed in hilly, dry land, with over 90% of the total sugarcane planting area lacking irrigation. While Guangxi, the main sugarcane-producing region, is a major production area in my country, it frequently suffers from seasonal droughts, especially spring droughts, leading to a significant reduction in seedling emergence rate after planting and severely impacting sugarcane yield. Although irrigation and other agricultural measures can partially alleviate drought, cultivating drought-resistant sugarcane varieties remains the fundamental way to address drought stress. Uneven natural rainfall leads to water shortages during the seedling emergence period after planting, resulting in low emergence rates, weak seedlings, and ultimately severe yield reductions, becoming one of the key abiotic stress factors restricting the stable development of my country's sugarcane industry. Drought stress during the period from planting to emergence significantly reduces the seedling emergence rate, and this stage is precisely where the existing sugarcane drought resistance evaluation system falls short.

[0003] Breeding and promoting drought-resistant sugarcane varieties is one of the most economical and effective strategies for addressing drought challenges. Currently, the identification and evaluation of sugarcane drought resistance largely focuses on drought stress experiments during the seedling or elongation stages after emergence. This involves subjecting sugarcane to drought stress treatment and observing plant growth indicators (such as chlorophyll content, proline accumulation, antioxidant enzyme activity, and relative water content) and physiological and biochemical parameters (such as chlorophyll content, proline accumulation, antioxidant enzyme activity, and relative water content) to screen for drought-resistant materials, thereby comprehensively evaluating the drought resistance of the materials. However, this method has two significant drawbacks: 1. Neglecting Drought Stress During the Seedling Stage: Existing sugarcane drought tolerance evaluation or identification systems do not fully consider the drought tolerance assessment of sugarcane seedlings during the critical stage from planting to emergence, and do not take into account the impact of drought stress on sugarcane varieties during this period. If spring drought occurs during this stage, insufficient soil moisture will directly lead to dehydration of seedling buds, delayed emergence, or even necrosis, resulting in a significant reduction in emergence rate, insufficient basic seedlings, and a substantial increase in the workload of replanting sugarcane later. Furthermore, this will lead to uneven sugarcane growth. This stage has not yet been included in the drought tolerance evaluation system, resulting in a blind spot in the selection of drought-resistant varieties. Evaluating drought tolerance only after emergence is incomplete and cannot truly reflect the full-cycle drought resistance of varieties in field production. As can be seen from existing technologies, there is currently a lack of identification methods specifically for the drought tolerance of sugarcane seedlings themselves.

[0004] 2. Insufficient complexity and applicability of the evaluation system: Traditional methods rely on multi-index detection (such as the determination of physiological and biochemical parameters). Although methods that rely on the determination of complex physiological indicators are scientific, they require expensive instruments and equipment, professional operators and long detection cycles. The process is cumbersome, inefficient, time-consuming and labor-intensive, costly and low-throughput. It is difficult to meet the actual needs of rapid and preliminary screening of a large number of germplasm resources in the early generations of breeding, and it is difficult to adapt to the needs of large-scale germplasm resource screening.

[0005] 3. Lack of attention to the germination characteristics of different bud positions on the seed stem: Current technology lacks the assessment of the differences in drought resistance of different parts of the seed stem (such as the upper, middle and lower buds of the rhizome) within the same variety. The germination characteristics of different bud positions on the seed stem not only directly affect the uniformity of seedling emergence in the field, but also have important practical significance for guiding farmers to scientifically select seed stems and improve sowing quality.

[0006] 4. Lack of evaluation on regional adaptability limitations: The existing drought resistance evaluation system does not take into account the ecological characteristics of frequent spring droughts in dry sugarcane areas in southern my country (such as Guangxi), which makes the selected varieties prone to yield reduction due to drought during the seed germination period in actual production.

[0007] To address the aforementioned issues, there is an urgent need to establish a drought resistance identification method that is specifically designed for identifying the drought resistance of sugarcane seed stalks during the germination period. This method should be simple to operate, rapid, efficient, and suitable for large-scale germplasm resource screening. It should also be able to accurately assess the differences in drought resistance characteristics among different parts of the same stalk, thereby compensating for the shortcomings of the existing drought resistance evaluation system. This would provide direct and effective technical support for drought-resistant sugarcane breeding and high-yield cultivation, and improve the stability of sugarcane production in arid areas. Summary of the Invention

[0008] To address the above shortcomings, this invention provides a method for rapid identification of drought resistance during the germination period of sugarcane seed stalks. This method is the first to systematically identify drought resistance during the germination period of sugarcane seed stalks, filling a technological gap in the identification of drought resistance during the critical period from planting to emergence. It solves the problem that existing sugarcane drought resistance evaluation or identification systems do not consider the impact of drought stress on sugarcane varieties during the period from planting to emergence. By eliminating interference from differences in bud position and initial physiological state, it can more accurately reflect the inherent genetic drought resistance of varieties, improving the accuracy and reliability of the identification results. This method is rapid, accurate, reliable, standardized, systematic, and highly operable, enabling precise assessment of differences in drought resistance characteristics at different parts of the same stalk. It solves problems in existing technologies such as the lack of drought resistance evaluation during the germination period, complex and inefficient methods with insufficient applicability, neglect of bud position differences, and lack of regional adaptability evaluation, achieving rapid, accurate, and standardized large-scale germplasm resource screening. The specific technical solution is as follows: A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; (5) Calculate drought resistance index and assess drought resistance level: assess drought resistance level based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk.

[0009] Preferably, the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes, in step (1), seed stalk selection and segmentation. Within 15 days after sugarcane harvest and before sowing, select healthy, undamaged and plump whole sugarcane seed stalks to be tested, and cut them longitudinally into 3 segments along the natural internodes. Mark the 1 / 3 segment near the tip, the 1 / 3 segment in the middle, and the 1 / 3 segment near the base of the root as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2 to 3 effective bud eyes, and the cut surface is coated with wood ash.

[0010] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, in step (1), the pretreatment involves soaking the sugarcane seed stalks in a 30-40 mg / L gibberellin solution for 23-24 hours, then treating them in an environment with a temperature of 20-25°C, humidity of 50-60% and ventilation for 24-25 hours, and then treating them at room temperature with a humidity of 40-45% for 8-10 hours.

[0011] This invention pretreats sugarcane seed stalks through a process of "wound protection → breaking dormancy → inducing stress resistance → state balancing," breaking dormancy before inducing stress resistance aligns with the natural germination process of seed stalks. Gibberellin is first used to break dormancy, transitioning the sugarcane seed stalks from a "dormant state" to a "germination preparation state." This avoids the problem of weak stress resistance induction and poor reproducibility caused by the seed stalks being in a dormant state (slow cell metabolism) and unable to effectively respond to drought stress (e.g., insufficient accumulation of osmotic regulators). Moderate drought (humidity 40-45%) can more efficiently activate the synthesis of stress resistance genes and osmotic regulators (such as proline), providing a more realistic response basis for subsequent drought stress. Treatment at 50-60% humidity before moderate drought stress avoids excessive water loss due to low humidity in the early stages (e.g., bud shrinkage), ensuring consistent initial physiological states across different bud segments and improving the reproducibility of drought resistance assessment.

[0012] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, in step (2), the field is flat, well-drained, and has sandy loam soil with an initial soil moisture content of 35-45%. A greenhouse is set up, and sugarcane is planted with a row spacing of 95-105mm, a plant spacing of 45-55mm, and shallow furrows 25-35mm deep. Each bud segment is placed flat in the furrow with the bud eye facing upward and covered with 18-21mm of fine soil.

[0013] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, in step (2), the drought stress duration is 14-20 days, and mild, moderate, and severe drought stresses are applied simultaneously to each seed stalk bud segment. The mild, moderate, and severe drought stresses account for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content under the mild, moderate, and severe drought stresses is controlled at 40-45%, 35-40%, and <35%, respectively.

[0014] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, in step (3), the monitoring of soil surface condition is carried out by using a simple hygrometer to detect soil moisture; the dynamic moisture regulation is: when the soil surface shows 0.5-1cm dry cracks and the water content is less than 35%, the soil is irrigated daily from 6:00 to 8:00 until the water content is 40%, only wetting the surface soil with a depth ≤2cm.

[0015] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, in step (4), irrigation is carried out by spraying once in the morning and once in the evening, with 290-310 mL per square meter each time, keeping the soil moist until seedling emergence; monitoring of seedling emergence begins on the 7th day after irrigation, counting the number of seedlings that have broken through the topsoil by 19-21 mm and whose first true leaf has fully unfolded, and counting for 3 consecutive days, recording the number of normally emerging buds and the total number of buds. The total number of buds refers to the number of buds that have successfully germinated (sprouted) among all bud segments after irrigation has resumed, that is, the number of buds that have broken through the topsoil (regardless of whether they have reached a specific height) or show signs of germination (such as the bud tip emerging) are all included. It reflects the "germination potential" of the sugarcane seed stalks and does not distinguish between the strength of germination ability.

[0016] The normal number of buds refers to the number of buds that meet the "high-quality germination" standard out of the total number of buds. It must meet the conditions of this application: "the buds break through the topsoil by 19-21 mm and the first true leaf is fully unfolded". This directly reflects the "stress resistance and stability" of the sugarcane seed stalk. Only the segments that can germinate and grow vigorously can be proven to be drought-resistant, stable and reliable seed stalks.

[0017] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seedlings, the calculation formulas for emergence rate and emergence uniformity in step (5) are: emergence rate (%) = (number of normal seedlings / total number of seedlings) × 100%; emergence uniformity (%) = [1 - (highest seedling height - lowest seedling height) / average seedling height] × 100%.

[0018] Preferably, in the method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, the drought resistance level is graded according to the following rules in step (5): High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0019] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period. Compared with the prior art, the beneficial effects of the present invention are: 1. This invention is the first to systematically identify the drought resistance of sugarcane seed stalks during the germination period, filling the existing technical gap in the identification of drought resistance during the seed stalk germination period, providing important technical support for the evaluation of drought resistance throughout the entire growth period, and solving the problem that the existing sugarcane drought resistance evaluation or identification system does not consider the impact of drought stress on sugarcane varieties during the period from sugarcane seed stalk planting to seedling emergence.

[0020] 2. The method of this invention divides a seed stalk into three segments—upper, middle, and lower—for simultaneous control experiments, which improves the identification efficiency. It also cleverly utilizes the biological characteristic of "bud heterogeneity" (apical dominance, uneven nutrient distribution, etc.) inherent in sugarcane seed stalks. Under the same external environmental stress, the differences in emergence of different bud segments of the same variety eliminate external environmental errors and purely reflect the drought resistance of buds in different parts of the variety, making the identification results more reliable. At the same time, this method also avoids the evaluation bias caused by a single bud segment (such as using only the middle bud segment), and the evaluation results can more comprehensively reflect the overall drought resistance of the sugarcane variety.

[0021] 3. This invention does not simply cut off soil water during drought stress, but instead conducts micro-sprinkler irrigation from 6:00 to 8:00 every day to simulate the morning dew of the spring drought season in southern China. This makes the breeding process as close as possible to the natural phenomenon of the spring drought season in southern China, but with a controllable mild drought-re-water cycle stress, in order to screen out sugarcane varieties that have the ability to survive and recover under real drought conditions. At the same time, it achieves precise control of mild-moderate-severe drought stress, making the identification process closer to the actual production environment, and the selected varieties are more practical and regionally adaptable.

[0022] 4. Many existing identification methods require human observation and judgment, while the method of this invention fully quantifies the control conditions, eliminates human judgment errors, and has stronger standardization and repeatability.

[0023] 5. This invention employs a dual pretreatment process combining environmental stress and hormone activation. The weak alkalinity of wood ash (primarily K₂CO₃) provides sterilization and preservation, reducing the risk of pathogen infection in the cut bud segments. Simultaneously, it promotes wound healing, increases bud germination rate, and eliminates the problem of reduced germination rate due to pathogen infection, thus leading to more accurate identification results. The pretreatment stage also utilizes gibberellin soaking to break the dormancy period of the seed stems, synchronizing the germination process of seed stems of different genotypes and eliminating the problem of inaccurate drought resistance evaluation results due to different seed stem dormancy periods.

[0024] 6. In this invention, sugarcane seed stalks are cut into sections and then treated at room temperature with a humidity of 40-45% (lower than the normal humidity for sugarcane storage, but not extremely dry) for 8-10 hours. This creates a moderately dry environment for the sugarcane, causing the seed stalks to lose water slightly. This serves as an "early warning signal" and gently induces the seed stalks to activate drought-resistant protection mechanisms (such as the initial accumulation of osmotic regulatory substances like proline). This initially activates the drought-resistant physiological mechanisms and provides a more realistic response basis for later drought stress.

[0025] 7. By eliminating interference from differences in bud position and initial physiological state, this invention can more accurately reflect the inherent genetic drought resistance of varieties, improving the accuracy and reliability of identification results. Compared with field full-growth-cycle identification or long-term stress in pots, this invention greatly shortens the time and provides a rapid, accurate, reliable, standardized, systematic, and highly operable method for identifying drought resistance in sugarcane during the germination period. This meets the needs of large-scale, rapid screening in the early stages of breeding and solves the problems existing in the prior art, such as neglecting drought stress in the seed stalk stage, insufficient complexity and applicability of the evaluation system, failure to pay attention to the germination characteristics of different bud positions on the seed stalk, and lack of evaluation with limited regional adaptability. Detailed Implementation

[0026] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0027] Example 1 A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; This also includes the selection and segmentation of seed stalks. Within 15 days after sugarcane harvest and before sowing, healthy, undamaged, and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 segments along the natural internodes. The 1 / 3 segment near the tip, the 1 / 3 segment in the middle, and the 1 / 3 segment near the base are marked as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2-3 effective buds, and the cut surface is coated with wood ash. The pretreatment involves soaking the sugarcane seed stalks in a 30 mg / L gibberellin solution for 23 hours, then treating them in an environment with a temperature of 20℃, a humidity of 50%, and ventilation for 24 hours, followed by treatment at room temperature with a humidity of 40% for 8 hours. (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; The field was prepared with flat, well-drained sandy loam soil with an initial soil moisture content of 35%. A greenhouse was erected, and sugarcane was planted with a row spacing of 95mm, a plant spacing of 45mm, and shallow furrows 25mm deep. Each bud segment was placed flat in the furrow with the bud facing upwards and covered with 18mm of fine soil. The drought stress period was 14 days. Mild, moderate, and severe drought stress were applied simultaneously to each seed bud segment, with the mild, moderate, and severe stresses accounting for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content for the mild, moderate, and severe drought stresses was controlled at 40%, 35%, and <35%, respectively. (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; The monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 0.5-1cm cracks and the moisture content is below 35%, the soil is re-irrigated at 6:00 every day to a moisture content of 40%, only wetting the surface soil with a depth ≤2cm. (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; Irrigation is carried out by spraying once in the morning and once in the evening, with 290 mL per square meter each time, keeping the soil moist until seedlings emerge. Seedling emergence is monitored starting on the 7th day after irrigation, counting when the seedlings have broken through 19 mm of the topsoil and the first true leaf has fully unfolded. This is done for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings. (5) Calculate drought resistance index and assess drought resistance level: Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk, assess the drought resistance level; The calculation formulas for emergence rate and emergence uniformity are: Emergence rate (%) = (Number of normal emergence buds / Total number of buds) × 100%; Emergence uniformity (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%; The drought resistance level is graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0028] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period.

[0029] Example 2 A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; This also includes the selection and segmentation of seed stalks. Within 15 days after sugarcane harvest and before sowing, healthy, undamaged, and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 segments along the natural internodes. The 1 / 3 of the seed stalk near the tip, the 1 / 3 of the middle, and the 1 / 3 of the seed stalk near the base are marked as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2-3 effective buds, and the cut surface is coated with wood ash. The pretreatment involves soaking the sugarcane seed stalks in a 40 mg / L gibberellin solution for 24 hours, then treating them in an environment with a temperature of 25℃, a humidity of 60%, and ventilation for 25 hours, followed by treatment at room temperature with a humidity of 45% for 10 hours. (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; The field was prepared with flat, well-drained sandy loam soil with an initial soil moisture content of 45%. A greenhouse was erected, and sugarcane was planted with a row spacing of 105mm, a plant spacing of 55mm, and shallow furrows 35mm deep. Each bud segment was placed flat in the furrow with the bud facing upwards and covered with 21mm of fine soil. The drought stress period was 20 days. Mild, moderate, and severe drought stress were applied simultaneously to each seed bud segment, with the mild, moderate, and severe stresses accounting for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content for the mild, moderate, and severe drought stresses was controlled at 45%, 40%, and <35%, respectively. (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; The monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 1cm cracks and the moisture content is below 35%, the soil is re-irrigated at 8:00 every day to a moisture content of 40%, only wetting the surface soil with a depth of ≤2cm. (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; Irrigation is carried out by spraying once in the morning and once in the evening, with 310 mL per square meter each time, keeping the soil moist until seedlings emerge. Seedling emergence is monitored starting on the 7th day after irrigation, counting when the seedlings have broken through 21 mm above the soil surface and the first true leaf has fully unfolded. This is done for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings. (5) Calculate drought resistance index and assess drought resistance level: Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk, assess the drought resistance level; The calculation formulas for emergence rate and emergence uniformity are: Emergence rate (%) = (Number of normal emergence buds / Total number of buds) × 100%; Emergence uniformity (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%; The drought resistance level is graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0030] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period.

[0031] Example 3 A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; This also includes the selection and segmentation of seed stalks. Within 15 days after sugarcane harvest and before sowing, healthy, undamaged, and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 segments along the natural internodes. The 1 / 3 segment near the tip, the middle 1 / 3 segment, and the 1 / 3 segment near the base are marked as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2-3 effective buds, and the cut surface is coated with wood ash. The pretreatment involves soaking the sugarcane seed stalks in a 32 mg / L gibberellin solution for 23.2 h, then treating them in a well-ventilated environment with a temperature of 21°C and a humidity of 52% for 24.2 h, and then treating them at room temperature with a humidity of 41% for 8.5 h. (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; The field was prepared with flat, well-drained sandy loam soil with an initial soil moisture content of 37%. A greenhouse was erected, and sugarcane was planted with a row spacing of 98mm, a plant spacing of 47mm, and shallow furrows 28mm deep. Each bud segment was placed flat in the furrow with the bud facing upwards and covered with 19mm of fine soil. The drought stress period was 15 days. Mild, moderate, and severe drought stress were applied simultaneously to each seed bud segment, with the mild, moderate, and severe stresses accounting for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content under the mild, moderate, and severe drought stresses was controlled at 41%, 36%, and <35%, respectively. (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; The monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 0.6cm cracks and the moisture content is below 35%, the soil is re-irrigated at 6:30 every day until the moisture content is 40%, only wetting the surface soil with a depth ≤2cm. (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; Irrigation is carried out by spraying once in the morning and once in the evening, with 295 mL per square meter each time, keeping the soil moist until seedlings emerge. Seedling emergence is monitored starting on the 7th day after irrigation, counting when the seedlings have broken through 19 mm of the topsoil and the first true leaf has fully unfolded. This is done for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings. (5) Calculate drought resistance index and assess drought resistance level: Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk, assess the drought resistance level; The calculation formulas for emergence rate and emergence uniformity are: Emergence rate (%) = (Number of normal emergence buds / Total number of buds) × 100%; Emergence uniformity (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%; The drought resistance level is graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0032] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period.

[0033] Example 4 A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; This also includes the selection and segmentation of seed stalks. Within 15 days after sugarcane harvest and before sowing, healthy, undamaged, and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 segments along the natural internodes. The 1 / 3 segment near the tip, the 1 / 3 segment in the middle, and the 1 / 3 segment near the base are marked as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2-3 effective buds, and the cut surface is coated with wood ash. The pretreatment involves soaking the sugarcane seed stalks in a 38 mg / L gibberellin solution for 23.8 h, then treating them in a well-ventilated environment with a temperature of 24℃ and a humidity of 58% for 24.8 h, and then treating them at room temperature with a humidity of 44% for 9.5 h. (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; The field was prepared with flat, well-drained sandy loam soil with an initial soil moisture content of 42%. A greenhouse was erected, and sugarcane was planted with a row spacing of 102mm, a plant spacing of 52mm, and shallow furrows 32mm deep. Each bud segment was placed flat in the furrow with the bud facing upwards and covered with 20mm of fine soil. The drought stress period was 19 days. Mild, moderate, and severe drought stress were applied simultaneously to each seed bud segment, with these three levels of stress accounting for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content under these three levels of stress was controlled at 44%, 39%, and <35%, respectively. (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; The monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 0.9cm cracks and the moisture content is below 35%, the soil is re-irrigated at 7:30 every day to a moisture content of 40%, only wetting the surface soil with a depth of ≤2cm. (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; Irrigation is carried out by spraying once in the morning and once in the evening, with 305 mL per square meter each time, keeping the soil moist until seedlings emerge. Seedling emergence is monitored starting on the 7th day after irrigation, counting when the seedlings break through 21 mm above the soil surface and the first true leaf is fully unfolded. This is done for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings. (5) Calculate drought resistance index and assess drought resistance level: Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk, assess the drought resistance level; The calculation formulas for emergence rate and emergence uniformity are: Emergence rate (%) = (Number of normal emergence buds / Total number of buds) × 100%; Emergence uniformity (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%; The drought resistance level is graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0034] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period.

[0035] Example 5 A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; This also includes the selection and segmentation of seed stalks. Within 15 days after sugarcane harvest and before sowing, healthy, undamaged, and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 segments along the natural internodes. The 1 / 3 segment near the tip, the 1 / 3 segment in the middle, and the 1 / 3 segment near the base are marked as the upper bud segment, the middle bud segment, and the lower bud segment, respectively. Each segment retains 2-3 effective buds, and the cut surface is coated with wood ash. The pretreatment involves soaking the sugarcane seed stalks in a 35 mg / L gibberellin solution for 23.5 h, then treating them in a well-ventilated environment with a temperature of 23°C and a humidity of 55% for 24.5 h, and then treating them at room temperature with a humidity of 43% for 9 h. (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; The field was prepared with flat, well-drained sandy loam soil with an initial soil moisture content of 38%. A greenhouse was erected, and sugarcane was planted with a row spacing of 100mm, a plant spacing of 50mm, and shallow furrows 30mm deep. Each bud segment was placed flat in the furrow with the bud facing upwards and covered with 20mm of fine soil. The drought stress period was 17 days. Mild, moderate, and severe drought stress were applied simultaneously to each seed bud segment, with these three levels of stress accounting for 5 / 8, 2 / 8, and 1 / 8 of the total drought stress time, respectively. The soil moisture content under these three levels of stress was controlled at 43%, 38%, and <35%, respectively. (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; The monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 0.8cm cracks and the moisture content is below 35%, the soil is re-irrigated at 7:00 every day to a moisture content of 40%, only wetting the surface soil with a depth of ≤2cm. (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; Irrigation is carried out by spraying once in the morning and once in the evening, with 300 mL per square meter each time, keeping the soil moist until seedlings emerge. Seedling emergence is monitored starting on the 7th day after irrigation, counting when the seedlings have broken through 20 mm of the topsoil and the first true leaf has fully unfolded. This is done for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings. (5) Calculate drought resistance index and assess drought resistance level: Based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk, assess the drought resistance level; The calculation formulas for emergence rate and emergence uniformity are: Emergence rate (%) = (Number of normal emergence buds / Total number of buds) × 100%; Emergence uniformity (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%; The drought resistance level is graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0036] Preferably, the application of the method described above in sugarcane drought-resistant breeding is used for screening drought-resistant varieties / lines during the sugarcane seed bud germination period.

[0037] Comparative Example 1 The difference from Example 1 is that the cut surface was not coated with wood ash, while other conditions remained the same.

[0038] Comparative Example 2 The difference from Example 1 is that the cut surface was coated with wood ash and soaked in gibberellin and left to stand before being subjected to drought stress treatment directly. There was no step of "then being placed at room temperature with 40% humidity for 8 hours" to perform moderate pre-drought stress treatment. Other conditions remained the same.

[0039] Comparative Example 3 The difference from Example 1 is that the pretreatment step does not involve soaking in gibberellin solution, while other conditions remain unchanged.

[0040] Comparative Example 4 The difference from Example 1 is that there is no pretreatment step, while other conditions remain the same.

[0041] Comparative Example 5 The difference from Example 2 is that the drought stress was not carried out in a gradient drought stress manner. All seed stem and bud segments were subjected to mild drought stress during the drought stress period, and the soil moisture content was controlled at 40-45%, while other conditions remained unchanged.

[0042] Comparative Example 6 The difference from Example 2 is that the drought stress was not carried out in a gradient drought stress manner. Instead, all seed stem and bud segments were subjected to moderate drought stress during the drought stress period, and the soil moisture content was controlled at 35-40%, while other conditions remained unchanged.

[0043] Comparative Example 7 The difference from Example 2 is that the drought stress was not carried out in a gradient drought stress manner. All seed stem and bud segments were subjected to severe drought stress during the drought stress period, the soil moisture content was controlled to be <35%, and other conditions remained unchanged.

[0044] Comparative Example 8 The difference from Example 2 is that the drought stress does not use two gradient drought stress methods of mild and moderate. The mild and moderate gradient drought stress accounts for 5 / 8 and 3 / 8 of the total drought stress time, respectively, and the soil moisture content is controlled at 43% and 38%, respectively, while other conditions remain unchanged.

[0045] Comparative Example 9 The difference from Example 2 is that the drought stress does not use two gradient drought stress methods of mild and severe. The mild and severe gradient drought stress account for 7 / 8 and 1 / 8 of the total drought stress time, respectively. The soil moisture content is controlled at 43% and <35%, respectively, while other conditions remain unchanged.

[0046] Comparative Example 10 The difference from Example 2 is that the drought stress does not use two gradient drought stress methods of moderate and severe. The moderate and severe gradient drought stress accounts for 7 / 8 and 1 / 8 of the total drought stress time, respectively. The soil moisture content is controlled at 38% and <35%, respectively, while other conditions remain unchanged.

[0047] Comparative Example 11 The difference from Example 3 is that there is no dynamic water regulation process in the dynamic drought stress control process, while other conditions remain unchanged.

[0048] Comparative Example 12 The difference from Example 5 is that only the upper bud segment was used for identification, while other conditions remained the same.

[0049] Comparative Example 13 The difference from Example 5 is that only the middle bud segment was used for identification, while other conditions remained the same.

[0050] Comparative Example 14 The difference from Example 5 is that only the lower bud segment was used for identification, while other conditions remained the same.

[0051] I. The impact of preprocessing on the results Using the main cultivated variety of sugarcane in Guangxi, Guitang 58, as the test material, 250 sections of Guitang 58 sugarcane seed stems (each section containing three bud segments, totaling 750 bud segments) were selected. These Guitang 58 sugarcane seed stems were randomly divided into 5 groups (50 sections per group, 3 replicates). The groups were treated according to Example 1 (complete pretreatment), Comparative Example 1 (no wood ash application), Comparative Example 2 (no pre-drought stress), Comparative Example 3 (no gibberellin soaking), and Comparative Example 4 (no pretreatment, only segmentation). The average value was taken as the result. Statistical indicators during the experiment included: bud segment infection rate (rot rate), normal emergence rate (the percentage of buds that broke through 19 mm of the topsoil and had their first true leaf unfolded), and germination synchronicity (the standard deviation of the difference in emergence time between different bud segments). Bud segment infection rate (rot rate) = (number of infected or rotten seed stalks / total number of seed stalks) × 100%; normal emergence rate (%) = (number of normally emerging buds / total number of buds) × 100%; germination synchronicity is the difference in emergence time between different bud segments. The experimental results are shown in Table 1 below.

[0052] Table 1. Results of experiments with different pretreatments on Guitang 58 seed stems As shown in Table 1, the experimental data indicates that applying wood ash effectively reduces the infection rate (rot rate) of bacteria and pathogens in sugarcane seed stalks and buds. This is because the weak alkalinity (K2CO3) of wood ash effectively kills bacteria and prevents decay, reducing the risk of pathogen infection after bud segment cutting. Pre-drought stress enhances sugarcane drought resistance; moderate pre-drought stress can induce the seed stalk to activate drought resistance protection mechanisms, accumulate osmotic regulators (such as proline) in advance, improve subsequent stress tolerance, and synchronize germination processes. Gibberellin soaking can break the dormancy of sugarcane seed stalks, making the germination time of different bud segments more consistent, avoiding deviations in drought resistance evaluation caused by dormancy differences.

[0053] II. The impact of gradient drought stress on the results Using the Yunnan Province's main drought-resistant variety Yunzhe 05-51 (known to have a germination rate >70% under natural drought conditions) as the test material, 1050 seed stalks (each containing three bud segments: upper, middle, and lower) were selected and randomly divided into 7 groups (150 stalks per group, 3 replicates). The groups were divided into Example 2 (mild, moderate, and severe drought stress), Comparative Example 5 (mild drought stress throughout), Comparative Example 6 (moderate drought stress throughout), Comparative Example 7 (severe drought stress throughout), Comparative Example 8 (no severe drought stress), Comparative Example 9 (no moderate drought stress), and Comparative Example 10 (no mild drought stress). The average value was taken as the result.

[0054] The emergence rate (upper / middle / lower), drought resistance level, number of misjudged buds (number of seedlings whose evaluation level did not match the gold standard), and misjudgment rate (using Example 2 as the gold standard) were statistically analyzed. Emergence rate (%) = (number of normally emerging buds / total number of buds) × 100%; Misjudgment rate = (number of seedlings in this group whose evaluation level did not match the gold standard / total number of seedlings in this group) × 100%; The gold standard was the multi-bud simultaneous evaluation result of Example 2; Drought resistance level was graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0055] The experimental results are shown in Table 2.

[0056] Table 2 As shown in Table 1, the multi-bud synchronous evaluation in Example 2 was rated as "high drought resistance," accurately determining the drought resistance level with a 0% misjudgment rate. This application demonstrates that gradient drought stress can truly reflect the drought resistance potential of sugarcane varieties. The emergence rate of each bud segment under gradient drought stress was the most balanced (difference ≤ 4%), indicating that gradient stress can more accurately reflect the inherent drought resistance of the variety.

[0057] The results of Comparative Examples 5-10 show that if sugarcane varieties are subjected to mild drought stress throughout the entire process, their germination rate will significantly decrease when encountering moderate or severe natural drought periods in actual production, making it impossible to truly distinguish between varieties that are "truly highly drought-resistant" and those that are "only mildly drought-resistant." If the entire process is subjected to moderate drought stress, uneven germination rates across different bud segments can also lead to misjudgments. If the entire process is subjected to severe drought stress (such extreme weather conditions are relatively rare in nature), it can lead to "false elimination" misjudgments, a method with a very high misjudgment rate. In the process of gradient drought stress, the lack of data on any stage of mild, moderate, or severe drought stress will result in misjudgments due to the absence of data on that stress level, creating an evaluation blind spot.

[0058] This invention utilizes a gradient drought stress model to simulate the dynamic process of spring drought in nature, thus accurately identifying the drought resistance of sugarcane. Single-process drought stress, due to its fixed intensity, leads to seedling emergence rates that deviate from the true drought resistance potential (too high or too low), resulting in a high misjudgment rate. Asymmetric gradient drought stress, lacking key drought stress gradients (such as severe or moderate), has evaluation blind spots and cannot comprehensively reflect the drought resistance of varieties, also leading to a high misjudgment rate. Therefore, gradient drought stress helps accurately identify the drought resistance of sugarcane seed buds during germination. Combined with simultaneous evaluation of multiple bud sites, it significantly reduces the misjudgment rate, accurately selecting sugarcane varieties with stable drought resistance. This effectively avoids the deviation of evaluation results from true drought resistance caused by single / non-gradient stress, which cannot cover actual drought variations in production.

[0059] III. The Impact of Dynamic Replenishment on Results Using sugarcane seed stalks of Guifu 98-296 (a highly drought-resistant variety) as the test material, 200 seed stalks (each containing three bud segments: upper, middle, and lower) were selected and randomly divided into two groups (100 seed stalks per group, with three replicates). The treatments were as follows: Example 3 (dynamic water regulation, dynamic irrigation) and Comparative Example 11 (no dynamic water regulation, i.e., no dynamic irrigation, natural water loss to cracking during drought stress). The emergence rate and uniformity of emergence were calculated. Emergence rate (%) = (number of normally emerging buds / total number of buds) × 100%; uniformity of emergence (%) = [1 - (highest seedling height - lowest seedling height) / average seedling height] × 100%. The experimental results are shown in Table 3 below.

[0060] Table 3 Dynamic irrigation, by simulating natural morning dew micro-spraying, maintained moderate soil moisture in the topsoil during drought stress, effectively alleviating bud dehydration stress and significantly improving emergence rate and uniformity. In contrast, the control group (Example 11) without dynamic irrigation suffered from persistent soil cracking, leading to germination obstacles and decreased uniformity, indicating that dynamic irrigation has a significant impact on sugarcane seed germination. This application, by mimicking natural morning dew micro-irrigation during drought stress, irrigating daily from 6:00 to 8:00 to 40% moisture content, makes the identification method as close as possible to the natural environment during sugarcane planting. By eliminating interference from differences in bud position and initial physiological state, it can more realistically reflect the inherent genetic drought resistance of the variety, improving the accuracy and reliability of the identification results.

[0061] IV. Reliability Verification of Simultaneous Evaluation of Multiple Bud Sites Three drought-resistant varieties were selected: Guifu 98-296 (strong drought resistance throughout the entire growth period), Yunzhe 14-368 (moderate drought resistance throughout the entire growth period), and Yuetang 00-236 (weak drought resistance throughout the entire growth period). Five treatment groups were set up for each variety, with 100 seed stalks per group (each stalk in Examples 4 and 5 contained three bud segments: upper, middle, and lower; Comparative Example 12 contained only upper bud segments; Comparative Example 13 contained only middle bud segments; and Comparative Example 14 contained only lower bud segments). The treatments were repeated three times, following the methods of Examples 4, 5, 12, 13, and 14 respectively. The emergence rate and uniformity of emergence were calculated as follows: Emergence rate (%) = (Number of normally emerging buds / Total number of buds) × 100%; Uniformity of emergence (%) = [1 - (Highest seedling height - Lowest seedling height) / Average seedling height] × 100%. Drought resistance levels were graded according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

[0062] The experimental results are shown in Table 4 below.

[0063] Table 4. Influence of different bud segments on drought resistance evaluation results. As shown in Table 4, the simultaneous evaluation of emergence rate and uniformity across multiple bud segments (upper, middle, and lower) effectively avoids misjudgments caused by the disadvantageous location or environmental interference of a single bud segment, and can accurately and reliably reflect the true drought resistance of sugarcane varieties. The advantages of simultaneous evaluation across multiple bud positions are particularly significant when evaluating weakly drought-resistant varieties, providing a scientific basis for early screening in sugarcane drought-resistant breeding.

[0064] This invention provides the first systematic identification of drought resistance during the germination period of sugarcane seed stalks, filling a technological gap in existing methods for identifying drought resistance during this stage. It addresses the problem that existing sugarcane drought resistance evaluation or identification systems do not consider the impact of drought stress on sugarcane varieties during the period from seed stalk planting to emergence. By eliminating interference from differences in bud position and initial physiological state, it more accurately reflects the inherent genetic drought resistance of the variety, improving the accuracy and reliability of the identification results. This invention provides a rapid, accurate, reliable, standardized, systematic, and highly operable method for identifying drought resistance during the germination period of sugarcane, solving problems in existing technologies such as neglecting drought stress during the seed stalk stage, insufficient complexity and applicability of the evaluation system, failure to consider the germination characteristics of different bud positions on the seed stalk, and lack of regional adaptability limitations.

[0065] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for rapid identification of drought resistance during the germination period of sugarcane seed stalks, characterized in that, Includes the following steps: (1) Seed stalk pretreatment: The upper, middle and lower bud segments of the sugarcane seed stalk are pretreated; (2) Drought stress: The pre-treated sugarcane seed stalks were planted in the reserved field, and drought stress was applied after sowing; (3) Dynamic drought stress control: During drought stress, soil surface conditions are monitored and dynamic water regulation is carried out; (4) Resumption of irrigation and seedling emergence monitoring: Irrigation was resumed after the drought stress ended, and seedling emergence was monitored; (5) Calculate drought resistance index and assess drought resistance level: assess drought resistance level based on the emergence rate and emergence uniformity data of the upper, middle and lower bud segments of the same sugarcane seed stalk.

2. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (1), the selection and segmentation of seed stalks are also included. Within 15 days after the sugarcane harvest and before sowing, healthy, undamaged and plump whole sugarcane seed stalks to be tested are selected and longitudinally cut into 3 sections along the natural internodes of the seed stalks. The 1 / 3 section near the tip of the seed stalk, the 1 / 3 section in the middle, and the 1 / 3 section near the base of the root are marked as the upper bud section, the middle bud section, and the lower bud section, respectively. Each section retains 2 to 3 effective bud eyes, and the cut surface is coated with wood ash.

3. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (1), the pretreatment involves soaking the sugarcane seed stalks in a 30-40 mg / L gibberellin solution for 23-24 hours, then treating them in a well-ventilated environment with a temperature of 20-25°C and a humidity of 50-60% for 24-25 hours, and then treating them at room temperature with a humidity of 40-45% for 8-10 hours.

4. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (2), the field is flat, well-drained, and has sandy loam soil with an initial soil moisture content of 35-45%. The greenhouse is set up, and the sugarcane is planted with a row spacing of 95-105mm, a plant spacing of 45-55mm, and shallow furrows 25-35mm deep. Each bud segment is placed flat in the furrow with the bud facing upwards and covered with 18-21mm of fine soil.

5. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (2), the drought stress duration is 14-20 days. Mild, moderate and severe drought stresses are applied simultaneously to each seed bud segment. The mild, moderate and severe drought stresses account for 5 / 8, 2 / 8 and 1 / 8 of the total drought stress time, respectively. The soil moisture content under the mild, moderate and severe drought stresses is controlled at 40-45%, 35-40% and <35%, respectively.

6. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (3), the monitoring of soil surface condition is achieved by using a simple hygrometer to detect soil moisture; the dynamic moisture control is as follows: when the soil surface shows 0.5-1cm dry cracks and the moisture content is less than 35%, the soil is re-irrigated from 6:00 to 8:00 every day until the moisture content reaches 40%, only wetting the surface soil with a depth ≤2cm.

7. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (4), the irrigation is sprayed once in the morning and once in the evening, with 290-310 mL per square meter each time, keeping the soil moist until the seedlings emerge; the seedling emergence is monitored starting on the 7th day after irrigation, counting the number of seedlings that have broken through the topsoil by 19-21 mm and whose first true leaf has fully unfolded, and counting for 3 consecutive days, recording the number of normal seedlings and the total number of seedlings.

8. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (5), the formulas for calculating the emergence rate and emergence uniformity are: emergence rate (%) = (number of normal seedlings / total number of seedlings) × 100%; emergence uniformity (%) = [1 - (highest seedling height - lowest seedling height) / average seedling height] × 100%.

9. The method for rapid identification of drought resistance during the germination period of sugarcane seed stalks according to claim 1, characterized in that: In step (5), the drought resistance level is classified according to the following rules: High drought resistance: the emergence rate of upper, middle and lower bud segments is ≥70%, and the uniformity of emergence is ≥70%; Moderately drought tolerant: the emergence rate of upper, middle and lower bud segments is ≥50% but <70%, or the emergence uniformity is 50-70%; Low drought tolerance: The emergence rate of any segment of the upper, middle, or lower buds is less than 50%, or the uniformity of emergence is less than 50%.

10. The application of the method according to any one of claims 1 to 9 in drought-resistant sugarcane breeding, characterized in that: It is used for screening drought-resistant varieties / lines during the germination period of sugarcane seed stalks.

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