Fraxinus mandshurica drought-resistant genotype selection method based on radial growth and application thereof

Abstract

The invention relates to a fraxinus mandshurica drought-enduring genotype selection method based on radial growth and application thereof. According to the method, the resistance, the restoring force and the restoring elastic force of the fraxinus mandshurica under the extreme drought event are calculated according to the sectional area increment (BAI) of the fraxinus mandshurica during the drought event and before and after the drought event. Comprehensively analyzing radial growth and ecological elasticity indexes of fraxinus mandshurica under drought events, and screening out fraxinus mandshurica genotypes with good radial growth and good drought resistance. According to the method, the drought-resistant excellent single plants naturally growing in the field can be screened out under the condition that tree growth is not affected, the method has important application value on fraxinus mandshurica improved variety breeding, and efficient, directional and accurate drought-resistant improved variety breeding can be achieved. The method is of great significance to directional breeding, introduction and development of fraxinus mandshurica and promotion of sustainable development of forestry.

Description

Technical Field

[0001] The invention belongs to the field of biotechnology, in particular to the technical field of plant genotype selection, and specifically relates to a novel method for selecting excellent drought-resistant genotypes of elm, and further discloses the selection method and application thereof. Background Art

[0002] Manchurian ash is a large deciduous tree of the genus Ash in the family Oleaceae. It has a straight trunk, a round and wide tree shape, beautiful texture, and strong adaptability. It is an excellent greening and ornamental tree species, an important building material and decorative material, and has high economic value and broad market prospects. With the development of industry, the continuous increase in the content of greenhouse gases in the atmosphere is one of the main factors causing the global temperature rise. The average surface temperature of the earth from 2011 to 2020 increased by 1.1℃ compared with the average temperature from 1850 to 1900. The increase is the largest in the northern region. Forests in some areas may benefit from climate change, but at the same time, the mortality rate of trees caused by drought will increase, and the growth of Manchurian ash is also affected by climate change. my country's natural Manchurian ash is mainly distributed in the northeast region. Due to previous over-cutting and failure to renew in time after cutting, the number of natural Manchurian ash has dropped sharply. The current market demand for Manchurian ash is huge, and the artificial cultivation cycle of Manchurian ash is relatively long. In order to alleviate the contradiction between supply and demand and meet market demand, it is particularly important to select Manchurian ash genotypes with excellent drought resistance under the background of global warming.

[0003] The traditional method of selecting drought-resistant genotypes of ash is mainly to collect seeds from superior trees, raise seedlings and plant trees, and after more than ten years or even decades of growth, investigate and analyze the growth traits to select excellent ash trees. The traditional method takes a long time and consumes a lot of manpower and material resources. There is also a method of subjecting ash seedlings to drought stress to select ash seedlings with excellent drought resistance. This method will affect the growth of seedlings, and it is impossible to know the drought resistance of the seedlings after they grow up.

[0004] The growth of trees in nature is not only affected by their own genetic factors, but also by the constraints of the external environment. Tree rings can retain strong climate signals, recording the impact of climate factors on tree growth during the tree growth cycle. When a drought event occurs, it will have an impact on the radial growth of trees. By screening out the genotypes of Manchurian ash with good drought resistance through its resistance, resilience and resilience under drought events, it is of great significance for the directional breeding of Manchurian ash. This technology can quickly and accurately screen out genotypes that have experienced drought stress and grown well in the wild, which greatly improves the breeding efficiency compared to the traditional breeding method of collecting seeds from natural superior plants and then evaluating them. Summary of the invention

[0005] In view of the current research status, the purpose of the present invention is to provide a method for selecting drought-resistant genotypes of ash mandshurica based on radial growth and its application, comprising the following steps:

[0006] (1) Determine historical drought events

[0007] First, obtain the historical meteorological data of the study area, which can be obtained through the Scientific Data Sharing Service Network of the China Meteorological Administration (http: / / data.cma.cn). The standardized precipitation evapotranspiration index (SPEI) used is calculated using the SPEI package in R language based on monthly average temperature and monthly precipitation. Divide the drought levels according to SPEI to determine the drought characteristic years: SPEI < -0.5 indicates no drought, -1.0 < SPEI ≤ -0.5 indicates light drought, -1.5 < SPEI ≤ -1.0 indicates moderate drought, -2.0 < SPEI ≤ -1.5 indicates severe drought, and SPEI ≤ -2.0 indicates extreme drought. Consecutive years of drought are regarded as a drought event.

[0008] (2) Determine whether tree growth is restricted in drought years

[0009] Use an increment borer to collect tree cores in two different directions at breast height (1.3 m) of healthy trees, passing through the pith. Mark the collected tree cores with specific information such as longitude and latitude coordinates, altitude, slope position, slope aspect, slope gradient, breast diameter, and tree height, and fix them after air drying. Polish them successively with 400-mesh, 600-mesh, 800-mesh, and 1000-mesh sandpapers until the tree rings are clearly visible. Use the skeleton method for visual cross-dating under a microscope, and measure the tree ring width with LinTab6 with a precision of 1 / 1000 mm combined with TASP-Win software. Use the COFFECHA program to check the dating and measurement results. Standardize them using ARSTAN software to make a standard chronology of tree ring width. Calculate its basal area increment (BAI) using R language. Match the radial growth of the trees with the drought characteristic years to determine whether the radial growth of the trees is restricted and narrow rings appear under drought events.

[0010] (3) Calculate the ecological resilience of Fraxinus mandshurica under drought events

[0011] Use the basal area increment (BAI) to calculate the resistance (Rt), resilience (Rc), and recovery elasticity (Rs) of Fraxinus mandshurica under drought events. Use the SPSS variance analysis method to analyze the differences in the resistance of Fraxinus mandshurica under drought events.

[0012] (4) Screen excellent drought-resistant genotypes based on radial growth

[0013] The wider the annual ring width of trees in the same year, the better the radial growth of elm. At the same time, combined with the ecological resilience of elm under extreme drought events, the greater the resistance (Rt) and the higher the recovery elasticity (Rs), the stronger its resistance to extreme drought and drought tolerance. Therefore, a comprehensive evaluation of the radial growth and ecological resilience (resistance, recovery elasticity) of elm under extreme drought events was conducted to screen out elm genotypes with excellent drought resistance.

[0014] The present invention also provides an application for selecting drought-resistant genotypes of Manchurian ash within a screening area.

[0015] The present invention has the following beneficial effects: the traditional method of selecting drought-resistant genotypes of elm mainly involves collecting seeds, raising seedlings and planting trees, and after more than ten years or decades of growth, investigating and analyzing the growth traits of trees to select excellent elm. This method has a long time period and consumes a lot of manpower and material resources. Alternatively, elm seedlings are subjected to drought stress for screening. This method not only affects the growth of seedlings, but also cannot tell how drought-resistant the seedlings are after they grow up. Using the present invention, first, the annual ring width data of large trees growing in the wild can be quickly obtained, and there is no need to do long-term seedling experiments, which saves experimental time and saves manpower, material and financial resources for the experiment. The information on tree growth obtained using long-term historical data is more convincing, reducing the errors caused by the accidental and random nature of short-term experiments. The use of this method can reduce the damage to trees, which is of great significance for the research of precious tree species.

[0016] The present invention is not limited by the age and growth environment of trees, and can more quickly, efficiently and accurately screen out genotypes with good drought resistance without affecting the normal growth of trees. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Collection of ash tree core samples

[0018] Figure 2 Reading the growth ring width

[0019] Figure 3 Changes of SPEI and radial growth of Fraxinus mandshurica in Maoershan area

[0020] Figure 4 The width of annual rings of ash trees narrows under drought events

[0021] Figure 5 Resistance, resilience and resilience of ash trees to drought events DETAILED DESCRIPTION

[0022] To better understand the present invention, the following further details the present invention in conjunction with embodiments and the accompanying drawings. However, those skilled in the art should understand that the following embodiments do not limit the protection scope of the present invention, and any changes and variations made based on the present invention fall within the protection scope of the present invention.

[0023] (1) Determination of historical drought events

[0024] Obtain the historical meteorological data of Maoershan area through the scientific data sharing service network of the China Meteorological Administration (http: / / data.cma.cn). The standardized precipitation evapotranspiration index (SPEI) adopted is calculated using the SPEI package in R language based on the monthly average temperature and monthly precipitation. Divide the drought levels according to SPEI to determine the drought characteristic years: SPEI < -0.5 indicates no drought, -1.0 < SPEI ≤ -0.5 indicates light drought, -1.5 < SPEI ≤ -1.0 indicates moderate drought, -2.0 < SPEI ≤ -1.5 indicates severe drought, and SPEI ≤ -2.0 indicates extreme drought. The years with consecutive droughts are regarded as a drought event. Drought events occurred in Maoershan area in 2000 and 2008.

[0025] (2) Determine whether tree growth is restricted in drought years

[0026] Collect tree cores: Select living Fraxinus mandshurica trees in Maoershan area for sample core collection. Drill 2 tree cores in the north-south direction at breast height (1.3 m), ensure that the pith is drilled through, and mark the detailed information of the core number, tree number, and habitat conditions.

[0027] Establish a chronology: Air-dry and fix the collected tree cores, and polish them successively with 400-mesh, 600-mesh, 800-mesh, and 1000-mesh sandpapers until the tree rings are clearly visible. Visually cross-date using the skeleton method under a microscope, measure the tree ring width with a LinTab6 tree ring analyzer with a precision of 0.001 mm, and check the dating and measurement results with the COFFECHA program. Standardize using the ARSTAN software to make a standard chronology of tree ring width.

[0028] Calculate the basal area increment (BAI): Use the dplr, treeclim, and dendroTools packages in R language to calculate the annual basal area increment of the tree. The formula is as follows:

[0029]

[0030] The code is as follows:

[0031]

[0032]

[0033] Determine that the radial growth of trees is limited under drought events: Match the radial growth of trees with the characteristic years of drought to determine that the radial growth of trees is affected under drought events. In the drought event in 2000, the cross-sectional growth of elm in the Maoershan area decreased by 19.6%. In the drought event in 2008, the cross-sectional growth of elm decreased by 15.4%. It can be seen that the drought event reduced the radial growth of elm in the Maoershan area ( Figure 3 , Figure 4 ).

[0034] (3) Calculation of ecological resilience under drought events

[0035] The resistance, resilience and resilience of each plant under drought events were calculated using the basal area increment. Figure 5 ). Resistance is the BAI of trees in the drought year divided by the average BAI of the three years before the drought; resilience is the average BAI of the three years after the drought divided by the BAI of trees in the drought year; resilience is the average BAI of the three years after the drought divided by the average BAI of the three years before the drought. The calculation formula is as follows:

[0036] Resistance(Rt)=BAIR / BAIpreR

[0037] Recovery(Rc)=BAIpostR / BAIR

[0038] Resilience(Rs)=BAIpostR / BAIpreR

[0039] Where: Rt represents resistance, Rc represents resilience, Rs represents recovery elasticity, BAIR represents the BAI in the year when the drought event occurs, BAIpreR represents the average BAI of the three years before the drought event, and BAIpostR represents the average BAI of the three years after the drought event.

[0040] (4) Selection of excellent drought-resistant genotypes based on radial growth:

[0041] The resistance, resilience and resilience of each single ash tree in Maoershan area under drought events were ranked, and combined with radial growth, excellent ash genotypes with good drought resistance were screened according to resistance, resilience and resilience (Table 1). It was found that 8 trees, LS32, LYL17, LS19, LS31, LYL2, LYL12, LS25, and LYL6, had strong resistance; 8 trees, LYL17, LS32, LS19, LS32, LYL10, LS25, LYL7, and LS22, had strong resilience; LYL17, LS32, LS19, LYL3, LYL17, LYL130, LS25, and LS31 had strong resilience. Overall, the four ash genotypes, LS32, LYL17, LS19, and LS25, had good drought resistance.

[0042] Table 1 Mean ecological resilience of elm trees under drought events in Maoershan area

[0043]

Claims

1. A method for selecting drought-resistant genotypes of ash mandshurica based on radial growth and its application, characterized in that: The method comprises the following steps: (1) Determine historical drought events (2) Determine whether tree growth is restricted in drought years (3) Calculation of ecological resilience of ash trees under drought events (4) Screening of excellent drought-resistant genotypes based on radial growth.

2. The method according to claim 1, characterized in that The method for determining the drought event in step (1) is to use the standardized precipitation evapotranspiration index to determine the drought characteristic year; if the drought characteristic year exceeds one year, the consecutive years are considered to be one drought event.

3. The method according to claim 1, characterized in that The method for determining the annual ring width of each genotype in step (2) is as follows: the sampled tree core is fixed on a customized wooden groove and polished with 400-mesh, 600-mesh and 800-mesh sandpapers respectively until the tree rings are clearly visible. The skeleton method is used for visual cross dating under a microscope, the annual ring width is measured using Lintab6 combined with TASP-Win software, and COFECHA is used for inspection.

4. The method according to claim 3, characterized in that The sampling method is growth cone sampling.

5. The method according to claim 1, characterized in that The ecological resilience described in step (3) is resistance, resilience and recovery elasticity.

6. The resistance, resilience and elasticity indicators according to claim 5 are determined by the BAI under the drought event and the BAI of the three years before and after the drought event.

7. The method according to claim 1, characterized in that The method for screening drought-resistant genotypes based on radial growth in step (4) is to determine the characteristic drought year and then the drought event according to local climate data, thereby finding the annual ring width of each genotype in the corresponding year, and obtaining the resistance, resilience and recovery elasticity of elm under drought events. After a comprehensive analysis of the above three indicators, the elm genotype with good drought resistance is selected.

8. Use of the method according to any one of claims 1 to 7 in genotype selection of woody plants.

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