Method for improving aroma of regenerated japonica rice

Abstract

This invention discloses a method for improving the aroma of regenerated fragrant rice. Belonging to the field of crop cultivation technology, this method significantly increases the content of the aroma compound 2-acetyl-1-pyrroline (2AP) in regenerated fragrant rice by simultaneously applying paclobutrazol or uniconazole (two plant growth regulators) during the tillering fertilizer application for the first-season fragrant rice, applying urea as a bud-promoting fertilizer before harvesting the first-season fragrant rice, and controlling the harvesting timing and stubble height of the first-season fragrant rice. Simultaneously, it can stabilize or increase the yield of fragrant rice, achieving stable or increased yield while improving the aroma. This invention is beneficial for improving the rice quality of regenerated fragrant rice and promoting its production.

Description

Technical Field

[0001] This invention belongs to the field of crop cultivation technology. More specifically, it relates to a method for improving the aroma of regenerated fragrant rice. Background Technology

[0002] Ratoon rice, as a highly efficient "one-plant-two-harvest" planting model, plays an important role in ensuring food security. With the increasing market demand for high-quality rice, applying fragrant rice varieties to ratoon rice cultivation to achieve a balance between "high yield" and "high quality" has become an urgent need for current agricultural development.

[0003] Aroma is an important indicator of rice quality. The aroma of fragrant rice is mainly determined by 2-acetyl-1-pyrroline (2AP), and its accumulation is heavily influenced by cultivation practices. However, the specific effects of different cultivation practices on the aroma of fragrant rice are unclear. Furthermore, existing research mainly focuses on the first-season fragrant rice, where aroma and yield often show a contrasting trend of one increasing and the other decreasing. There are no reports on which cultivation practices can be adjusted to achieve a synergistic effect and overcome the technical bottleneck of simultaneously increasing yield and enhancing aroma in ratooned fragrant rice. While there are numerous reports on methods to increase the yield of ratooned rice, methods to improve the aroma of ratooned fragrant rice are lacking, or the improvement is limited and requires further development. For example, patent application CN119371244A discloses a foliar fertilizer specifically for ratooned fragrant rice. Spraying this foliar fertilizer after the first-season fragrant rice harvest can increase the content of aroma substances in ratooned fragrant rice, but the increase is less than 50%.

[0004] In ratooning rice cultivation systems, stubble height is a key factor influencing axillary bud germination, yield composition, and rice quality. Different stubble heights determine the number of regenerated buds, their growth vigor, and nutrient sources. However, existing research on stubble height primarily focuses on its impact on ratooning rice yield; the mechanisms by which it specifically regulates the synthesis and accumulation of 2AP in ratooning aromatic rice remain unclear. Chemical regulation is a common method in crop cultivation used to shape plant architecture, improve stress resistance, and increase yield. Although plant growth regulators such as paclobutrazol and uniconazole have been used in rice production, their application is mostly concentrated in the seedling stage or the early vegetative growth stage of the first crop, primarily acting to control excessive vegetative growth and promote tillering. There are no reports of combining them with tillering fertilizers for the first crop to indirectly influence aroma formation in the ratooning season by regulating the early growth and development of the first crop. Furthermore, the application of existing technologies in ratooning rice systems also focuses on the germination period of regenerated buds or the growth regulation of the ratooning season, with no reports of intervention starting from the source of the first crop (such as the tillering stage).

[0005] Currently, there is still a lack of methods to significantly improve the aroma of regenerated fragrant rice, as well as to stabilize or increase its yield while improving the aroma. Furthermore, it is unclear how to solve the problem of the difficulty in achieving both yield and aroma in existing regenerated fragrant rice. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention provides a method for improving the aroma of regenerated fragrant rice.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] Based on previous experimental results and our own research experience, this invention provides a method to enhance the aroma of regenerated fragrant rice by controlling and adjusting cultivation measures from the initial planting stage. Compared with the control group, the content of aroma compounds (2AP) in regenerated fragrant rice cultivated using this method can be increased by more than 70%, significantly improving the aroma and quality of the rice. Therefore, this invention seeks protection for the method for enhancing the aroma of regenerated fragrant rice.

[0009] This invention provides a method for improving the aroma of regenerated fragrant rice, comprising the following steps: S1. Raise seedlings of fragrant rice, and after the seedlings are raised, transplant them to the paddy field to complete the sowing of the first season of fragrant rice; S2. When applying tillering fertilizer to the first crop of fragrant rice, apply paclobutrazol or uniconazole at the same time; S3. Apply urea 10-15 days before the first harvest of fragrant rice; S4. Harvest the first-season fragrant rice when 82%–86% of the grains are fully ripe and yellow, leaving stubble at a height of 10–30 cm. S5. Apply urea and potassium chloride, or urea and compound fertilizer, 7-10 days after the first harvest of fragrant rice; the compound fertilizer contains N, P2O5 and K2O in a ratio of 14-16:14-16:14-16. S6. Routine water and fertilizer management until harvest of ratooned fragrant rice.

[0010] Optionally, in S2, the tillering fertilizer used is the same tillering fertilizer used in the conventional cultivation of fragrant rice.

[0011] In a specific embodiment of the present invention, the tillering fertilizer used is a compound fertilizer; in the compound fertilizer, the content ratio of N, P2O5 and K2O is 14-16:14-16:14-16.

[0012] More specifically, the tillering fertilizer used is a compound fertilizer; in the compound fertilizer, the content ratio of N, P2O5 and K2O is 15:15:15.

[0013] Specifically, in S2, the application concentration of paclobutrazol or uniconazole is 10–30 g / mu.

[0014] Preferably, in S2, the application concentration of paclobutrazol or uniconazole is 10-15 g / mu.

[0015] More preferably, in S2, the application concentration of paclobutrazol or uniconazole is 10 g / mu.

[0016] Specifically, in S3, urea is applied 10 to 12 days before the first harvest of fragrant rice.

[0017] More specifically, in S3, urea is applied as a germination-promoting fertilizer 10 days before the first harvest of fragrant rice.

[0018] Specifically, in S3, the application concentration of urea is 6–9 kg / mu.

[0019] Preferably, in S3, the application concentration of urea is 7-8 kg / mu.

[0020] More preferably, in S3, the application concentration of urea is 7.5 kg / mu.

[0021] Specifically, in S4, the first-season fragrant rice is harvested and stubble is left when 84% to 86% of the grains are fully ripe and yellow.

[0022] More specifically, in S4, the first-season fragrant rice is harvested and stubbled when 85% of the grains are fully ripe and yellow.

[0023] Specifically, in S4, the height of the pile is 10–25 cm.

[0024] Preferably, in S4, the height of the pile is 15-25 cm.

[0025] More preferably, in S4, the height of the pile is 15 cm.

[0026] Specifically, in S5, urea and potassium chloride, or urea and compound fertilizer, are applied 7-8 days after the first harvest of fragrant rice.

[0027] More specifically, in S5, urea and potassium chloride are applied as seedling fertilizer 7 days after the first harvest of fragrant rice, or urea and compound fertilizer are applied as seedling fertilizer.

[0028] Specifically, in S5, the application concentration of urea is 6-9 kg / mu, the application concentration of potassium chloride is 4-6 kg / mu, and the application concentration of compound fertilizer is 14-16 kg / mu.

[0029] Preferably, in S5, the application concentration of urea is 7-8 kg / mu, the application concentration of potassium chloride is 4.5-5.5 kg / mu, and the application concentration of compound fertilizer is 14.5-15.5 kg / mu.

[0030] More preferably, in S5, the application concentration of urea is 7.5 kg / mu, the application concentration of potassium chloride is 5 kg / mu, and the application concentration of compound fertilizer is 15 kg / mu.

[0031] Specifically, in the compound fertilizer, the content ratio of N, P2O5, and K2O is 15:15:15.

[0032] Specifically, the fragrant rice variety is either Qingxiangyou 19 or Meixiangzhan 2.

[0033] Specifically, the method for improving the aroma of regenerated fragrant rice is a method for increasing the content of the aroma substance 2-acetyl-1-pyrrolidine in regenerated fragrant rice.

[0034] The present invention has the following beneficial effects: This invention provides a method for improving the aroma of regenerated fragrant rice. The method significantly increases the content of the aroma compound 2-acetyl-1-pyrrolline in regenerated fragrant rice by simultaneously applying paclobutrazol or uniconazole (two plant growth regulators) during the tillering fertilizer application for the first-season fragrant rice, applying urea as a sprouting fertilizer before harvesting the first-season fragrant rice, and controlling the timing of harvesting and stubble height. Simultaneously, it stabilizes or increases the yield of fragrant rice, achieving stable or increased production while enhancing the aroma. This invention is beneficial for improving the quality of regenerated fragrant rice, promoting its production, and ensuring food security. Detailed Implementation

[0035] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0036] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0037] Example 1: Effect of Stubble Height on 2AP Content in Regenerated Fragrant Rice The experiment described in this embodiment was conducted in 2023 at the Guangzhou Experimental Base in Guangdong Province. The tested varieties were the high-quality fragrant rice varieties Qingxiangyou 19 and Meixiangzhan 2.

[0038] The experiment included three stubble height treatments: 5 cm, 15 cm, and 25 cm. All treatments employed the same field management practices, with water and fertilizer management conducted according to local customs and no plant growth regulators applied. The first-season fragrant rice was harvested and stubbled when 85% of the grains were fully ripe. Stubble was left at three heights: 5 cm, 15 cm, and 25 cm. Grain samples were collected after the second-season fragrant rice matured, and the content of 2-acetyl-1-pyrrololine (2AP) was determined by gas chromatography-mass spectrometry (GC-MS).

[0039] The effect of stubble height on the 2AP content of ratooned fragrant rice is shown in Table 1. Table 1 shows that when the stubble height is 15 cm, the 2AP content in Qingxiangyou 19 and Meixiangzhan 2 ratooned fragrant rice varieties reached 184.74 μg / kg and 152.59 μg / kg, respectively, both significantly higher than other treatments. When the stubble height is 5 cm, the 2AP content in both varieties is the lowest, at 133.26 μg / kg and 103.63 μg / kg, respectively. When the stubble height increases to 25 cm, the 2AP content, although slightly higher than the 5 cm treatment, is still significantly lower than the 15 cm treatment. These results indicate that compared to traditional low stubble (0–10 cm) or excessively high stubble (>20 cm), controlling the stubble height at 15 cm most effectively promotes the accumulation of aroma compounds in ratooned fragrant rice, creating optimal conditions for the synthesis of the aroma compound 2AP, and ensuring a significant and stable increase in aroma compound content. In terms of yield, the appropriate stubble height significantly increased the yield of the ratooning season (ratoon fragrant rice). Both varieties showed higher yields at stubble heights of 15 cm and 5 cm, with the 15 cm treatment yielding significantly higher than the 25 cm treatment, while there was no significant difference in yield between the 5 cm and 15 cm treatments.

[0040] Table 1. Effect of stubble height on 2AP content in ratooned fragrant rice

[0041] Note: Different lowercase letters in the table indicate significant differences. p <0.05.

[0042] Example 2: Effect of application of plant growth regulators during the tillering stage of first-season fragrant rice on the 2AP content of ratooned fragrant rice. The experiment described in this embodiment was conducted in 2024 at the Guangzhou Experimental Base in Guangdong Province. The tested varieties were the high-quality fragrant rice varieties Qingxiangyou 19 and Meixiangzhan 2. Based on the determination that 15 cm is the optimal stubble height, the effects of applying different concentrations of plant growth regulators on the 2AP content of the regenerated fragrant rice were investigated, in addition to applying tillering fertilizer during the tillering stage of the first-season fragrant rice.

[0043] Two plant growth regulators, paclobutrazol and uniconazole, were used in the experiment, with four dosage gradients of 0, 10, 20, and 30 g / mu for each. All treatments were simultaneously applied at the tillering stage of the first-season rice crop, with the corresponding dosage of plant growth regulator mixed evenly with tillering fertilizer (the tillering fertilizer used in this invention was a compound fertilizer, applied at a rate of 24 kg / mu; the compound fertilizer contained nitrogen (N), phosphorus (P2O5), and potassium (K2O) in a ratio of 15:15:15). Field management was carried out according to the same plan during the ratoon season. Grain samples were taken after the ratoon season rice matured, and the 2AP content was determined using GC-MS.

[0044] The effects of plant growth regulator application during the tillering stage of first-season fragrant rice on the 2AP content of ratooned fragrant rice are shown in Table 2. Table 2 shows that for Qingxiangyou 19 fragrant rice, the highest 2AP content (285.42 μg / kg) was obtained when paclobutrazol was applied at a rate of 10 g / mu, significantly higher than the control group without paclobutrazol (253.50 μg / kg). When the paclobutrazol dosage was increased to 20 g / mu and 30 g / mu, the 2AP content in the ratooned fragrant rice decreased to 266.32 μg / kg and 273.35 μg / kg, respectively. The same trend was observed when uniconazole was applied, with the best effect observed at a dosage of 10 g / mu (265.64 μg / kg). The experimental results of Meixiangzhan No. 2 further verified this pattern. Both plant growth regulators achieved the highest 2AP content (paclobutrazol 241.78 μg / kg, uniconazole 223.90 μg / kg) at a dosage of 10 g / mu, and the 2AP content decreased with increasing dosage. Regarding yield, the application of different types and dosages of plant growth regulators during the first tillering stage showed a high-concentration inhibitory effect on the yield of both varieties in the regenerative season; however, a dosage of 10 g / mu had no significant inhibitory effect on yield.

[0045] The above results indicate that applying paclobutrazol or uniconazole at a rate of 10 g / mu during the first tillering stage is the best chemical regulation strategy to enhance the aroma of regenerated fragrant rice. Too high or too low a rate will not achieve the optimal effect.

[0046] Table 2. Effects of plant growth regulator application during the tillering stage of first-season fragrant rice on the 2AP content of ratooned fragrant rice.

[0047] Note: Different lowercase letters in the table indicate significant differences. p <0.05.

[0048] Example 3: Effects of Staged Fertilizer Management on 2AP Content in Regenerated Fragrant Rice The experiment described in this embodiment was conducted in 2024 at the Guangzhou Experimental Base in Guangdong Province. The tested varieties were the high-quality fragrant rice varieties Qingxiangyou 19 and Meixiangzhan 2. Based on the determination that 15 cm is the optimal stubble height, the effects of staged fertilizer management on the 2AP content of ratooned fragrant rice were investigated.

[0049] The experiment consisted of four treatments: Treatment 1: Conventional fertilization (control); Treatment 2: Sprouting fertilizer alone, i.e., 7.5 kg / mu of urea applied 10 days before the first harvest of fragrant rice; Treatment 3: Seedling-promoting fertilizer alone, i.e., 7.5 kg / mu of urea and 15 kg / mu of compound fertilizer (with a nitrogen (N), phosphorus (P2O5), and potassium (K2O) ratio of 15:15:15) applied 7 days after the first harvest of fragrant rice; Treatment 4: Combination of sprouting fertilizer and seedling-promoting fertilizer, i.e., the fertilization operations of the first two treatments were performed simultaneously. No plant growth regulators were used in any of the treatments, and other field management practices remained consistent. Grain samples were collected after the ratoon season of fragrant rice matured, and the 2AP content was determined by GC-MS.

[0050] The effects of staged fertilizer application on the 2AP content of ratooning fragrant rice are shown in Table 3. Table 3 shows that for Qingxiangyou 19, the ratooning fragrant rice with the highest 2AP content (297.62 μg / kg) obtained by applying both bud-promoting and seedling-enhancing fertilizers was significantly higher than that obtained by conventional fertilization (251.36 μg / kg), bud-promoting fertilizer alone (272.17 μg / kg), and seedling-enhancing fertilizer alone (281.94 μg / kg). For Meixiangzhan 2, the ratooning fragrant rice with the highest 2AP content (162.24 μg / kg) obtained by applying both bud-promoting and seedling-enhancing fertilizers was also significantly higher than that obtained by conventional fertilization (120.15 μg / kg), bud-promoting fertilizer alone (139.83 μg / kg), and seedling-enhancing fertilizer alone (131.11 μg / kg), consistent with the results of Qingxiangyou 19. The above results indicate that while applying either the bud-promoting fertilizer or the seedling-enhancing fertilizer alone can increase the 2AP content in ratooned fragrant rice, the combined application of both has the best effect, demonstrating that the bud-promoting fertilizer and the seedling-enhancing fertilizer have a significant synergistic effect in promoting aroma synthesis in different fragrant rice varieties. In terms of yield, phased fertilizer application significantly increased yield, and for both varieties, the treatment with combined bud-promoting and seedling-enhancing fertilizers yielded the highest yield. Furthermore, the yield of the treatment with only a single phase of fertilizer (bud-promoting fertilizer or seedling-enhancing fertilizer) was also significantly higher than that of conventional fertilization.

[0051] Table 3. Effects of staged fertilizer application on 2AP content in ratooned fragrant rice.

[0052] Note: Different lowercase letters in the table indicate significant differences. p <0.05.

[0053] Example 4: Effects of integrated cultivation practices on the 2AP content of ratooned fragrant rice The experiment described in this embodiment was conducted in 2025 at the Guangzhou Experimental Base in Guangdong Province. The Qingxiangyou 19 fragrant rice variety was used as the experimental material to systematically evaluate the synergistic effect of stubble height, application of plant growth regulators during the tillering stage of the first season of fragrant rice, and phased fertilizer management on the aroma of regenerated fragrant rice.

[0054] The experiment included five treatments: Treatment 1: Current farming practices, i.e., stubble height of 5 cm, no plant growth regulators applied, and conventional fertilization (control); Treatment 2: Stubble height of 15 cm, no plant growth regulators applied, and conventional fertilization; Treatment 3: In addition to the 15 cm stubble height, a combination of bud-promoting and seedling-enhancing fertilizers were applied; Treatment 4: In addition to Treatment 3, 10 g / mu of paclobutrazol was applied (simultaneously with tillering fertilizer during the tillering stage of the first-season fragrant rice); Treatment 5: In addition to Treatment 3, 10 g / mu of either paclobutrazol or uniconazole was applied (simultaneously with tillering fertilizer during the tillering stage of the first-season fragrant rice). Field management practices remained consistent across all treatments during the ratoon season. Grain samples were collected after the ratoon season fragrant rice matured, and the 2AP content was determined using GC-MS.

[0055] The effects of integrated cultivation measures on the 2AP content of ratooning rice are shown in Table 4. As shown in Table 4, under the same management conditions, the 2AP content in ratooning rice treated with a 15 cm stubble height (175.77 μg / kg) was significantly higher than that of the current farming practices (156.85 μg / kg). When bud-promoting fertilizer and seedling-enhancing fertilizer were applied in addition to the 15 cm stubble height (treatment 3), the 2AP content in the ratooning rice further increased to 193.69 μg / kg, demonstrating the positive effect of fertilizer management. Based on treatment 3, treatments 4 and 5, which added paclobutrazol and uniconazole respectively, further increased the 2AP content in the ratooning rice, reaching 252.04 μg / kg and 271.23 μg / kg, respectively. In terms of yield, a 15 cm stubble height combined with staged fertilization (including bud-promoting and seedling-enhancing fertilizers) can significantly increase yield. Furthermore, the addition of plant growth regulators (paclobutrazol or acetamiprid) on this basis can maintain the yield at the same high level. The yields of the three treatments (treatments 3, 4, and 5) are significantly higher than those of treatments with a 5 cm stubble height and no fertilization (treatment 1) and treatments with a 15 cm stubble height and only conventional fertilization (treatment 2).

[0056] The above results fully demonstrate that combining appropriate stubble height (15 cm), optimized fertilizer management (promoting bud growth fertilizer + seedling growth fertilizer) and chemical regulation during the first tillering period (paclobutrazol or uniconazole) can produce a significant synergistic effect, which is the best cultivation model to achieve the goal of "increasing yield and enhancing aroma" in regenerated fragrant rice.

[0057] Table 4. Effects of integrated cultivation practices on 2AP content in ratooned fragrant rice.

[0058] Note: Different lowercase letters in the table indicate significant differences. p <0.05.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for enhancing the aroma of regenerated fragrant rice, characterized in that, Includes the following steps: S1. Raise seedlings of fragrant rice, and after the seedlings are raised, transplant them to the paddy field to complete the sowing of the first season of fragrant rice; S2. When applying tillering fertilizer to the first crop of fragrant rice, apply paclobutrazol or uniconazole at the same time; S3. Apply urea 10-15 days before the first harvest of fragrant rice; S4. Harvest the first-season fragrant rice when 82%–86% of the grains are fully ripe and yellow, leaving stubble at a height of 10–30 cm. S5. Apply urea and potassium chloride, or urea and compound fertilizer, 7-10 days after the first harvest of fragrant rice; the compound fertilizer contains N, P2O5 and K2O in a ratio of 14-16:14-16:14-16. S6. Routine water and fertilizer management until harvest of ratooned fragrant rice.

2. The method according to claim 1, characterized in that, In S2, the application concentration of paclobutrazol or uniconazole is 10–30 g / mu.

3. The method according to claim 1, characterized in that, In S3, the application concentration of urea is 6–9 kg / mu.

4. The method according to claim 1, characterized in that, In S4, the height of the pile is 10-25 cm.

5. The method according to claim 1, characterized in that, In S5, the application concentration of urea is 6-9 kg / mu, the application concentration of potassium chloride is 4-6 kg / mu, and the application concentration of compound fertilizer is 14-16 kg / mu.

6. The method according to claim 2, characterized in that, In S2, the application concentration of paclobutrazol or uniconazole is 10-15 g / mu.

7. The method according to claim 3, characterized in that, In S3, the application concentration of urea is 7-8 kg / mu.

8. The method according to claim 4, characterized in that, In S4, the height of the pile is 15-25 cm.

9. The method according to claim 5, characterized in that, In S5, the application concentration of urea is 7-8 kg / mu, the application concentration of potassium chloride is 4.5-5.5 kg / mu, and the application concentration of compound fertilizer is 14.5-15.5 kg / mu.

10. The method according to any one of claims 1 to 9, characterized in that, The fragrant rice varieties mentioned are Qingxiangyou 19 or Meixiangzhan 2.

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