USE OF DELAYED DORMANT APPLICATIONS OF HOMOBRASSINOLIDE ON GRAPES TO ENHANCE BUD BREAK

Abstract

We disclose methods to enhance bud breaking in grapes. Unfavorable bud breaking is caused by insufficient dormancy, which itself is commonly caused by insufficiently cold or long winters. Insufficient dormancy results in apical dominance which lessens the number of branches and fruiting sites. We have discovered that treatment with the plant growth regulator homobrassinolide enhances great growth uniformity and bud-break uniformity similar to Hydrogen Cyanamide without the negative effects.

Claims

1. A solution for enhancing bud break in plants comprising a plant growth regulator selected from the group consisting of Homobrassinolide, brassinolide, epibrassinolide, castasterone, and 28-homocastasterone.

2. The solution of claim 1 in which said the concentration of the plant growth regulator is between 1 part per million and 2 parts per million.

3. A method for enhancing bud break in plants comprising the steps of treating plants following delay dormant stage with a solution comprising a plant growth regulator selected from the group consisting of Homobrassinolide, brassinolide, epibrassinolide, castasterone, and 28-homocastasterone at a concentration of between 1 part per million and 2 parts per million.

4. A method for enhancing bud break in plants comprising the steps of treating plants at bud swell stage with a solution comprising a plant growth regulator selected from the group consisting of Homobrassinolide, brassinolide, epibrassinolide, castasterone, and 28-homocastasterone at a concentration of between 1 part per million and 2 parts per million.

5. The solution of claim 1 in which the plant growth regulator is homobrassinolide.

6. The solution of claim 1 in which the solution is comprised of 1-2 ppm homobrassinolide.

7. The method of claim 3 in which the plant growth regulator is homobrassinolide.

8. The method of claim 3 in which the solution is comprised of 1-2 ppm homobrassinolide

Description

BRIEF DESCRIPTION OF THE FIGURES

[0015] FIG. 1 is the chemical structure of homobrassinolide.

[0016] FIG. 2 is the chemical structure of brassinolide.

[0017] FIG. 3 is the chemical structure of epibrassinolide.

[0018] FIG. 4 is the chemical structure of castasterone.

[0019] FIG. 5 is the chemical structure of 28-homocastasterone.

[0020] FIG. 6 is a table of results of homobrassinolide trials on bud break uniformity.

[0021] FIG. 7 is a chart illustrating the effects of homobrassinolide on bud break uniformity.

DETAILED DESCRIPTION OF THE SUBJECT MATTER

[0022] The following description and referenced figures illustrate embodiments of the subject matter of this application. They are not intended to limit the scope of the claims. Those familiar with the art may recognize that other embodiments of the disclosed method are possible. All such alternative embodiments should be considered within the scope of the application's claims.

[0023] Applicant discloses methods of using homobrassinolide (HBR FIG. 1) as a rest breaking agent comparable to Hydrogen Cyanamide in efficacy. HBR can be applied dormant and delayed dormant without crop injury. Delayed dormant application allows the deciduous crop to accumulate maximum chilling, which is particularly useful in years of warm winters. Other related plant growth regulating molecules such as brassinolide (FIG. 2), epibrassinolide (FIG. 3), castasterone (FIGS. 4), and 28-homocastasterone (FIG. 5) are hypothesized to have similar efficacy.

[0024] A portion of an established commercial vineyard was used for the study. The HBR (FIG. 1) treatments were replicated down a single row and arranged in sets of 3 vines per plot. Plots were flagged with colored ribbon to identify the treatments and there were 4 replicates each. Spray applications were made when the vines were still dormant on Day 0 (Feb. 12, 2019) or during the delayed dormant period, when buds were swollen or at eraser stage, on Day 24 (Mar. 8, 2019)). Specific details on the spray applications and a test site description are shown in Table 1. Fruit and foliage were observed for symptoms of phytotoxicity periodically during the trial at each evaluation interval. Crop injury was rated using a scale of 0-10, where 0=no injury and 10=100% of tree injured. Percentage bud break was evaluated by counting numbers of shoots from 30 nodes on fruiting canes from trunk to trunk and 5 renewal spurs were chosen non-systematically on Day 34 (Mar. 18, 2019) and Day 41 (Mar. 25, 2019).

[0025] Statistical differences were highly significant and variability in the data was low. Having waited until approximately 55 chill portions (a quantification of the aggregate low temperature exposure needed for a crop to break dormancy), the dormant sprays allowed both the Hydrogen Cyanamide (Dormex) treated and untreated vines to accumulate the maximum chilling. HBR at label rates of 1 part per million active ingredient (ppm ai) and 2 ppm ai applied at early bud swell was as effective as the standard rate of Dormex or 5 ppm ai HBR applied in the dormant period compared to the untreated check. HBR applied delayed dormant at 5 ppm appeared to have been too high based on effects being statistically equivalent to the untreated check 34 days after application (DAA). By 41 DAA, bud break in plots treated with the rest breaking agents had peaked and were statistically greater than the untreated check, which did not reach 100% bud break. Uniformity was enhanced by both Dormex and 5 ppm ai HBR applied as a dormant spray. Variability was lowest in the untreated check by 41 DAA even though bud break had not reached 90%. It is not unusual for bud break to exceed 100% because secondary shoots were stimulated by the effects of overcoming apical dominance by both effective rest breaking and the accumulation of maximum chilling by untreated vines. FIGS. 6 and 7.

[0026] Effects on spur bud break were not as strong as observed on fruiting canes and did not reach 100% by 41 DAA in any treatment, including the Dormex standard treatment. However, the results were statistically significant between the rest breaking treatments as a group compared to the untreated check at both evaluation intervals. In addition, by 41 DAA, the effects of 2 ppm ai HBR applied at bud swell were also equivalent to the untreated check. It appeared that spur bud break had peaked by 34 DAA because by 41 DAA, percentages were mostly the same. Only the untreated check continued to break buds, which remained approximately 15% lower than the rest breaking treatments as a group.

[0027] Treatment with homobrassinolide also increased number of shoots by overcoming apical dominance from either dormant or delayed dormant spray applications.

[0028] HBR treatments of 1 ppm ai, 2 ppm ai, or 5 ppm ai increased shoots compared to control and both 1 ppm ai and 1 ppm ai treatments were comparable to the Hydrogen Cyanamide standard treatment.

[0029] Treatment with HBR has several advantages to the standard Hydrogen Cyanamide treatment:

[0030] 1. Dormex (Hydrogen Cyanamide) is a synthetic chemical with reported toxicity due to acute exposure while HBR is a naturally occurring plant hormone with a non-toxic mode of action.

[0031] 2. HBR is biodegradable, leaves no residue, and is environmentally safe (Source: label for 0.1% HBR) whereas Hydrogen Cyanamide is not readily biodegradable (Source: SDS from Alzchem).

[0032] 3. As disclosed in the specification, HBR is active in the nano molar to pico molar range, whereas approximately 20,000 times the amount of Hydrogen Cyanamide is needed approach the effect of HBR.

[0033] 4. Repeated use of Hydrogen Cyanamide over the years can lower the fruitability of vines by as much as 20-30% per year whereas HBR has no such effect. See US2016016859 paragraph 008. HBR has been shown to improve plant stress tolerance, flowering, fruit growth, and overall quality of crops. Repeated use of HBR may cause stress thus affecting the crop yield.

[0034] 5. Dormex can damage nearby crops whereas there is no evidence that HBR has harmful effects on nearby crops (https://journals.ashs.org/horttech/abstract/journals/horttech/26/6/article-p839.xml)

[0035] 6. HBR also has multiple biological actions besides enhancing bud breaking that are often desired such as enhanced ripening, fruit firmness, and disease resistance.

[0036] 7. Dormex can be phytotoxic in grapes and other fruit crops whereas HBR has been found to be non-phytotoxic. Dormex can be acutely toxic when misused.