Methods to induce heat stress tolerance in plants

Abstract

To provide methods of improving heat stress tolerance in plants.SOLUTION: A method for improving heat stress tolerance in plants, comprising applying an effective amount of 1-amino-1-cyclopropanecarboxylic acid (ACC) to the plant, wherein the plant is selected from the group consisting of wheat, corn, soybean, cotton, tomato, Brassica napus, bean, lettuce, turf grass, and ornamental plants.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention is directed to a method for improving heat stress tolerance in plants, comprising applying an effective amount of 1-amino-1-cyclopropanecarboxylic acid to the plants. [Background technology]

[0002] Temperatures are rising worldwide and are expected to continue to rise through the rest of this century. This increase in temperature will cause heat stress in crops such as wheat. See Tack J., et al., Effect of warming temperatures on US wheat yields Proc Natl Acad Sci US A. 2015 Jun 2;112(22):6931-6. Heat stress poses a particular threat to wheat production when stress occurs during the reproductive and grain-filling stages. See Ababaei B. and Chenu K., Heat shocks increasingly impede grain filling but have little effect on grain setting across the Australian wheatbelt, Agr. For. Meterol., 2020 Jan; 284, 107889.

[0003] Heat stress is thought to limit a plant's metabolic rate and damage chloroplasts, thereby reducing the plant's ability to photosynthesize. This reduction in photosynthetic capacity results in reduced grain yields. Reduced grain yields are costly for both farmers and the overall population. As the world's population grows, increased crop production is necessary. Therefore, improving heat stress tolerance in crops such as wheat is both beneficial and necessary for the survival of the world's population.

[0004] 1-Amino-1-cyclopropanecarboxylic acid ("ACC") is a product of the enzyme ACC synthase and serves as a biosynthetic precursor of ethylene in plants. Ethylene has been shown to be involved in several plant responses, such as stress, fruit set, leaf abscission, flowering, and senescence. Due to its role as an ethylene precursor, ACC has been used in agriculture to induce ethylene response phenomena. However, ACC has not been shown to induce heat stress tolerance in various plants, including wheat, corn, soybean, cotton, tomato, bean, lettuce, rapeseed (e.g., canola, rapeseed), turfgrass, and ornamental plants. In fact, heat stress-induced ethylene production in developing wheat grains causes fertility problems and reduced yield. See Hays DB et al., Heat stress-induced ethylene production in developing wheat grains induces kernel abortion and increased maturation in a susceptible cultivar, Plant Sci, 2007, 172, 1113-1123 and Valluru R., et al., Phenotypic and genome-wide association analysis of spike ethylene in diverse wheat genotypes under heat stress, New Phytologist, 2016, doi:10.1111 / nph.14367, 1-13.

[0005] Therefore, there is a need in the art for methods to improve heat stress tolerance in crops. Summary of the Invention

[0006] The present invention is directed to a method for improving heat stress tolerance in plants, comprising applying an effective amount of 1-amino-1-cyclopropanecarboxylic acid ("ACC") to the plants, wherein the plants are selected from the group consisting of wheat, corn, soybean, cotton, tomato, rapeseed, bean, lettuce, turfgrass, and ornamental plants. DETAILED DESCRIPTION OF THE INVENTION

[0007] Applicants have unexpectedly discovered that application of 1-amino-1-cyclopropanecarboxylic acid ("ACC") to plants improves heat stress tolerance and results in increased crop yields.

[0008] Once planted, plants go through life stages such as vegetative, reproductive, maturation, and senescence. Plants are generally subject to heat stress during the vegetative, vegetative, and reproductive stages, especially the flowering stage. Plants can also be subject to heat stress during the maturation stage.

[0009] Wheat, in particular, goes through several life cycle stages, beginning with germination, followed by tillering, heading, flowering, and finally maturity. See Miller TD, Growth Stages of Wheat: Identification and Understanding Improve Crop Management, Texas A&M Agrilife Ext. SCS-1999-16. The Feekes scale was developed to systematically describe the life cycle of wheat plants. Feekes stage 1 describes the emergence of the wheat plant from the soil. Feekes stages 2-3 describe the tillering stage, which is when the plant produces axillary or lateral buds known as bristles. Wheat plants begin to produce bristles at Feekes stage 2 and cease producing bristles at Feekes stage 3. Feekes stage 4 describes the onset of upright growth in wheat plants. Feekes stage 5 occurs after a period of low temperature and determines the number of spikelets per spike. An ear emerges from the tip of each spikelet and produces multiple spikelets, each of which is fertile. Spikelets that form after stage 5 do not result in a grain harvest. During Feekes stages 6-9, nodes develop and leaves appear. Feekes stage 10 marks the beginning of heading and flowering. Feekes stage 10 is divided into several substages. Feekes stage 10.1 describes the appearance of the tip of the ear. Feekes stage 10.3 describes the appearance of half the ear. Feekes stage 10.4 describes the appearance of three-quarters of the ear. Feekes stage 10.5 describes the full appearance of the ear. Flowering begins at Feekes stage 10.5.1. This is followed by pollination and kernel (i.e., grain) maturation from Feekes stage 10.5.3 to Feekes stage 11.4.

[0010] Applicant refers to soybean developmental stages as "V" stages throughout this application. The "V" stages are designated numerically as V1, V2, V3, etc. In this V(n) identification system, (n) represents the number of open trifoliate leaflets. Each leaf stage is defined by the top leaf being fully expanded.

[0011] As used herein, the term "heat stress" is defined as exposure of a plant to temperatures above 24°C. In preferred embodiments, the term "heat stress" may include exposure of a plant to temperatures above 25°C, above 26°C, above 27°C, above 28°C, above 29°C, or above 30°C. Heat stress may occur either during the day or at night. For the same plant, nighttime heat stress may occur at lower temperatures than daytime heat stress.

[0012] As used herein, the term "enhance" is defined as an increase in growth and / or yield of a plant exposed to heat stress. Growth and / or yield measurements include, but are not limited to, measurements taken during the vegetative growth phase, such as fresh weight of biomass, total number of reproductive tillers, percentage of reproductive tillers, canopy density, and total dry weight of biomass, and measurements taken during the reproductive phase, such as, but not limited to, total number of panicles, panicle weight, yield per panicle, grain weight, and harvest index.

[0013] As used herein, all numerical values relating to amounts, ratios, weight percent, and the like are defined as "about" the respective particular value, plus or minus 10%. For example, the phrase "at least 5.0% by weight" should be understood as "at least 4.5% to 5.5% by weight." Thus, amounts within 10% of any claimed numerical value are encompassed within the scope of the claim.

[0014] The term "effective amount" refers to the amount of formulation that will improve heat stress tolerance. An "effective amount" will vary depending on, among other factors, the type of plant being treated, the severity of the heat stress, the desired outcome, and the life stage of the plant being treated. Therefore, it is not always possible to specify an exact "effective amount."

[0015] The articles "a," "an," and "the" are intended to include the plural as well as the singular, unless the context clearly dictates otherwise. For example, some methods of the invention are directed to ameliorating heat stress in "wheat," but may encompass control of multiple wheat plants (e.g., two or more wheat plants or two or more wheat species, etc.).

[0016] In one embodiment, the present invention is directed to a method for improving heat stress tolerance in a plant, comprising applying an effective amount of ACC to the plant, wherein the plant is selected from the group consisting of wheat, corn, soybean, cotton, tomato, rapeseed, bean, lettuce, turfgrass, and ornamental plants.

[0017] Brassica napus includes all its varieties, subspecies and varieties, such as, but not limited to, annual rape, Argentine canola, canola, colza, Hanover salad, oilseed rape, rapeseed, rape kale, rutabaga, Siberian kale, summer rape, swede, Swede rape, Swedish turnip and winter rape. In a preferred embodiment, the Brassica napus variety is canola.

[0018] In a preferred embodiment, the plant is selected from the group consisting of wheat, corn, soybean, cotton, tomato, rapeseed, bean, lettuce, and turfgrass. In a more preferred embodiment, the plant is selected from the group consisting of wheat, corn, soybean, cotton, tomato, rapeseed, bean, and lettuce. In an even more preferred embodiment, the plant is wheat, lettuce, soybean, or rapeseed.

[0019] In preferred embodiments, the effective amount of ACC is from about 1 to about 1,000 parts per million ("ppm"), more preferably from about 1 to about 500 ppm, even more preferably from about 10 to about 300 ppm, even more preferably from about 30 to about 300 ppm, and most preferably from about 30 to about 100 ppm.

[0020] In another preferred embodiment, ACC is applied to the plants at a rate of about 0.001 to about 1,000 grams per hectare ("g / HA"), more preferably about 0.028 to about 281 g / HA, and even more preferably about 0.28 to about 28 g / HA.

[0021] The method of the present invention contemplates applying ACC to the plant at any stage of the plant's development. In a preferred embodiment, ACC is applied to the plant during the plant's developmental, vegetative and / or reproductive stages, including the flowering stage.

[0022] In another preferred embodiment, ACC is applied to the wheat plants from Feekes stage 2 to Feekes stage 11, even more preferably from Feekes stage 2 to Feekes stage 5, or from Feekes stage 10 to Feekes stage 11, even more preferably at Feekes stage 5, or from Feekes stage 10.4 to 10.5.

[0023] In another preferred embodiment, ACC is applied to said lettuce plants during the vegetative stage, more preferably during the heading stage, also known as the rosette stage.

[0024] In another preferred embodiment, ACC is applied to said soybean plants during the vegetative stage, more preferably from the V1 to V4 stage.

[0025] In another preferred embodiment, ACC is applied to said rapeseed plants at the reproductive stage, more preferably at the flowering stage.

[0026] The ACC of the present invention can be applied by any convenient means. Those skilled in the art are familiar with application methods such as, but not limited to, spraying, brushing, dipping, infloor application, drip irrigation, drenching, sprenching, dusting, powdering, granules, seed treatment, pressurized liquid (aerosol), fogging, or side dressing. In a preferred embodiment, the ACC is applied to the plant as a spray, and even more preferably as a foliar spray.

[0027] These exemplary embodiments are in no way limiting and are set forth merely to illustrate some aspects of the present invention.

[0028] Additionally, the following examples are offered by way of illustration only and not by way of limitation. [Example]

[0029] Example 1 - Heat stress tolerance in wheat after ACC application at flowering stage method Twenty-four pots of Apogee wheat were grown in a greenhouse under three successive growth conditions. First, the wheat was planted in ProMix® growth medium and grown in a growth cabinet for approximately six weeks under a 24 / 18°C day / night temperature and a 16 / 8-hour light / dark photoperiod. After the first set of growth conditions, the plants were at Feekes stage 10.4-10.5 (flowering stage). Next, a spray application of 0, 30, or 100 ppm ACC (n=8) was performed using a tank sprayer. Two days after treatment, the plants were then transferred to a growth chamber for seven days under a 36 / 30°C day / night temperature and a 16 / 8-hour light / dark photoperiod. These conditions constitute significant heat stress. Finally, the plants were returned to the growth chamber for approximately five more weeks under a 24 / 18°C day / night temperature and a 16 / 8-hour light / dark photoperiod. Plants were then destructively harvested and the total number of ears, ear weight, kernel weight, yield per ear, delta ear number, and harvest index were measured. Delta ear number was calculated by subtracting the number of reproductive tillers at treatment from the number of reproductive tillers at harvest. An increase in reproductive tillers indicates increased reproductive success. Harvest index was calculated by dividing pounds of grain by total pounds of aboveground biomass. The results are shown in Table 1 below. [Table 1]

[0030] result As shown in Table 1 above, application of ACC prior to heat stress resulted in increases in panicle number, panicle weight, kernel weight, yield per panicle, tiller number, and harvest index. These increases were dose-dependent. Specifically, application of 30 ppm ACC increased panicle number by 6.3%, panicle weight by 8.5%, kernel weight by 15.7%, yield per panicle by 11.1%, tiller number by 16.7%, and harvest index by 10.3% compared to the control. Application of 100 ppm ACC increased panicle number by 10.5%, panicle weight by 14.5%, kernel weight by 25.7%, yield per panicle by 17.8%, tiller number by 42.0%, and harvest index by 17.2% compared to the control. Therefore, application of ACC at the wheat flowering stage protected wheat from subsequent heat stress and increased yield and reproductive success compared to wheat not treated with ACC.

[0031] Example 2 - Heat stress tolerance in wheat after ACC application at Weekes stage 5 method Apogee wheat was sown in ProMix BX (Premier Horticulture) and grown in a growth cabinet under the following conditions: a day / night temperature of 24 / 18°C and a 16 / 8-hour light / dark photoperiod. After the first set of growth conditions on November 15, 2019, plants were evaluated at the 5-month stage. A track sprayer was then used to spray 0, 0, or 100 ppm ACC (n=8). Two days after treatment, one set of control plants ("treated control") and 100 ppm ACC plants were then transferred to a second growth cabinet for four days under a day / night temperature of 34 / 28°C and a 16 / 8-hour light / dark photoperiod. These conditions constitute significant heat stress. Another set of control plants ("stress control") remained in the first growth cabinet. Finally, the plants were then returned to the first growth cabinet for approximately 14 days to allow the plants to reach Feekes stage 10.1 (heading). The plants were then destructively harvested and the total number of ears, fresh weight, total number of reproductive tillers, percentage of reproductive tillers, delta colony density, and total dry weight were measured. The percentage of reproductive tillers was calculated by dividing the number of reproductive tillers by the total number of ears at harvest. The delta colony density was calculated by subtracting the colony density at treatment from the colony density at harvest. The results are shown in Table 2 below. [Table 2]

[0032] result As shown in Table 2 above, application of ACC prior to heat stress resulted in increases in fresh weight, total tiller number, % tillers, delta canopy density, and total dry weight compared to wheat plants exposed to heat stress but not treated with ACC. The % reproductive tillers were restored to within 1.1% of wheat plants grown under ideal conditions (i.e., stress control). Furthermore, delta canopy density increased by 42.1% in ACC-treated wheat plants compared to wheat plants grown under ideal conditions. Therefore, application of ACC during the vegetative stage of wheat protected wheat from subsequent heat stress and increased yield and reproductive success compared to heat-stressed wheat not treated with ACC.

[0033] Example 3 - Heat stress tolerance in wheat after ACC application at Weekes stage 5 method Apogee wheat was sown in ProMix BX (Premier Horticulture) and grown in a growth cabinet under the following conditions: a day / night temperature of 24 / 18°C and a 16 / 8-hour light / dark photoperiod. After the first set of growth conditions, the plants were at Feekes stage 5. They were then spray-treated with 0, 0, 100, or 300 ppm ACC (n=8) using a track sprayer on October 4, 2019. Two days after treatment, one set of control plants ("treated control") and 100 ppm ACC plants were transferred to a second growth cabinet for four days under a day / night temperature of 34 / 28°C and a 16 / 8-hour light / dark photoperiod. These conditions constitute significant heat stress. Another set of control plants ("stress control") remained in the first growth cabinet. Finally, the plants were then returned to the first growth cabinet for approximately 14 days to allow the plants to reach Feekes stage 10.1 (heading). The plants were then destructively harvested and the total number of ears, fresh weight, total number of reproductive tillers, percentage of reproductive tillers, delta colony density, and total dry weight were measured. The percentage of reproductive tillers was calculated by dividing the number of reproductive tillers by the total number of ears at harvest. The delta colony density was calculated by subtracting the colony density at treatment from the colony density at harvest. The results are shown in Table 3 below. [Table 3]

[0034] result As shown in Table 3 above, application of 100 ppm ACC prior to heat stress resulted in increased panicle number, fresh weight, total tiller number, delta canopy density, and total dry weight compared to wheat plants exposed to heat stress but not treated with ACC. Application of 300 ppm ACC prior to heat stress resulted in increased panicle number and total dry weight. Therefore, application of ACC during the vegetative stage of wheat protected wheat from subsequent heat stress and increased yield compared to heat-stressed wheat not treated with ACC.

[0035] Example 4 - Heat stress tolerance in lettuce after ACC application at the rosette stage method Butterhead lettuce was sown in ProMix BX (Premier Horticulture) and grown in a greenhouse. Three weeks after sowing, the lettuce was transferred to a growth cabinet under the following conditions: a day / night temperature of 24 / 18°C and a 16 / 8-hour light / dark photoperiod. After the first set of growth conditions, the plants reached the rosette stage. Population density was calculated four days after transfer. Next, a track sprayer was used to spray 0, 10, 30, or 100 ppm ACC (n=5) on September 21, 2020. Two days after treatment, half of the plants were transferred to a second growth cabinet for 9 days under a day / night temperature of 34 / 30°C and a 16 / 8-hour light / dark photoperiod. These conditions constitute significant heat stress. The plants were then destructively harvested, and fresh weight, size, population density, and delta population density were measured. Delta population density is calculated by subtracting the population density at treatment from the population density at harvest. The results are shown in Table 4 below. [Table 4]

[0036] result As shown in Table 4 above, application of 10, 30, or 100 ppm ACC prior to heat stress resulted in increases in fresh weight, canopy density, and delta canopy density compared to lettuce plants exposed to heat stress but not treated with ACC. Therefore, application of ACC during the vegetative stage of lettuce protected the lettuce from subsequent heat stress and increased yield compared to heat-stressed lettuce not treated with ACC.

[0037] Example 5 - Heat stress tolerance in soybean after ACC application method Williams 82 soybeans were sown in ProMix BX (Premier Horticulture) and grown in a greenhouse. When soybean plants exhibited a fully expanded first trifoliate leaf (V1 growth stage), soybean canopy density was measured and grouped into treatments and replicates based on relative size. A track sprayer was then used to spray 0, 10, 30, or 100 ACC (n=5) on October 9, 2020. After spraying, the plants were transferred to a growth cabinet under the following conditions: a day / night temperature of 24 / 18°C and a 16 / 8-hour light / dark photoperiod. Three days after treatment, half of the plants were then transferred to a second growth cabinet for 6 days under a day / night temperature of 34 / 30°C and a 16 / 8-hour light / dark photoperiod. These conditions constitute early heat stress. The plants were then destructively harvested and measured for fresh weight, canopy density, delta canopy density, total dry weight, and height. The results are shown in Table 5 below. [Table 5]

[0038] result As shown in Table 5 above, application of 10 and 30 ppm ACC prior to heat stress resulted in increases in fresh weight, canopy density, delta canopy density, total dry weight, and height compared to soybean plants exposed to heat stress but not treated with ACC. Application of 100 ppm ACC prior to heat stress resulted in an increase in total dry weight. Therefore, application of ACC during the vegetative stage of soybean protected soybeans from subsequent heat stress and increased yield compared to heat-stressed soybeans not treated with ACC.

[0039] Example 6 - Heat stress tolerance in rapeseed after ACC application method Dwarf varieties of Brassica napus, commonly used as an experimental model for canola varieties, were sown in ProMix BX (Premier Horticulture) and grown in a greenhouse. Six days after the Brassica napus plants began to flower, they were sprayed with 0, 10, 100, or 300 ppm ACC (n=10) using a track sprayer. After spraying, the plants were transferred to a growth cabinet under the following conditions: a day / night temperature of 24 / 18°C and a 16 / 8-hour light / dark cycle. Two days after treatment, half of the plants were then transferred to a second growth cabinet for 7 days under a day / night temperature of 36 / 30°C and a 16 / 8-hour light / dark photoperiod. These conditions constitute early heat stress. Flowers and pods were regularly pruned to maintain a pod count of approximately 10. The plants were then destructively harvested and seed yield, seed number, seed yield per pod, seed number per pod and seed weight were determined, the results of which are shown in Table 6 below. [Table 6]

[0040] result As shown in Table 6 above, application of 30, 100, or 300 ppm ACC prior to heat stress resulted in increased seed yield per pod and seed number per pod compared to heat-stressed, non-ACC-treated B. napus plants. Application of 10 ppm ACC prior to heat stress resulted in increased seed number per pod. Therefore, application of ACC early in the reproductive development of B. napus dwarf plants protected the plants from later heat stress and increased yield compared to heat-stressed B. napus dwarf plants not treated with ACC.

Claims

1. 1. A method for improving heat stress tolerance in a plant, comprising applying an effective amount of 1-amino-1-cyclopropanecarboxylic acid (ACC) to the plant, wherein the plant is selected from the group consisting of cotton, tomato, bean, turfgrass, and ornamental plants.

2. The method of claim 1 , wherein the plant is turfgrass.

3. The method of claim 1 , wherein the plant is a tomato.

4. The method of claim 1 , wherein the plant is cotton.

5. 10. The method of claim 1, wherein the effective amount is from about 1 to about 1000 ppm.

6. 10. The method of claim 1, wherein the effective amount is from about 10 to about 300 ppm.

7. 10. The method of claim 1, wherein the effective amount is from about 30 to about 300 ppm.

8. 10. The method of claim 1, wherein the effective amount is from about 30 to about 100 ppm.

9. 10. The method of claim 1, wherein the effective amount is from about 10 to about 100 ppm.

10. 10. The method of claim 1, wherein the effective amount is from about 10 to about 30 ppm.

11. The method of claim 1 , wherein the ACC is applied to the plant as a spray.

12. 12. The method of claim 11, wherein the ACC is applied to the plant as a foliar spray.

13. 10. The method of claim 1, wherein the ACC is applied to the plant during the plant's developmental stage.