DESC:Field of the Invention:
The present invention is in the field of ¬biomass energy generation and sericulture. The Invention in particular provides a method for inducing early, rapid and uniform bud break and growth in mulberry plants.
Background of the Invention:
The following background discussion includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Sericulture is a very important domestic industry in many countries. Sericulture is the process of cultivating silkworms and extracting silk from them. The caterpillars of the domestic silkmoth (also called ‘Bombyx mori’) are the most commonly used silkworm species in sericulture. Other types of silkworms (such as Eri, Muga, and Tasar) are also cultivated for the production of ‘wild silks’.
The mulberry (Morus alba L.), a commercially important perennial system, requires periodic pruning to regenerate vegetative growth. In India, most of the mulberry cultivation falls under arid or semi-arid conditions, where the plants are routinely exposed to intermittent drought that adversely affects foliage production. In India, mulberry cultivation is practiced under rainfed as well as irrigated conditions. There are two major traditional practices of harvesting foliage for silkworm rearing, one being individual leaf harvesting and second shoot-harvesting.

Bud break is a natural phenomenon in trees to re-activate growth in response to favorable changes in the environment. Trees enter the growth arrest stage called dormancy, as an adaptive
strategy to survive the unfavorable environmental conditions. In temperate trees, bud break is triggered after winter dormancy, while in tropical trees, these phenological events mostly depend on water availability. In plants, under unfavorable conditions like desiccation stress, one of the earliest responses is the accumulation of abscisic acid (ABA), an endogenous growth hormone. ABA is a long-distance signaling hormone which is generally transported from roots to shoots resulting in growth arrest. In addition to ABA, ethylene also has key role in triggering the induction of bud dormancy and repressing bud activity, thereby delaying bud break, while gibberellin (GA) induce dormancy release. Under stress, buds accumulate high levels of ABA, which arrests bud break and further growth. Therefore, it is likely that the buds from the plants grown under ideal conditions would exhibit early and rapid bud break compared to those from the drought stressed plants.

Timely leaf production is a major constraint in sericulture. One of the determinants of this multifactorial trait is number of shoots (Vijayan et al. 2014), in turn determined by the number of buds opened at a time. Individual leaf picking or shoot harvesting is followed for foliage harvest while under irrigated conditions, the cultivated genotypes can be harvested once in 70 days from an established plantation (Datta et al. 2002). Bud break after pruning has a critical role in meeting timely foliage demand, wherein apical dominance has a key role in regulating the lateral branch growth, thus controlling foliage growth.

In mulberry, 6-benzyl aminopurine (BAP) and Thidiazuron (TDZ) could induce rapid bud break in in-vitro studies (Tewari et al. 1999) and in general, in perennial trees, different growth regulators/mild stress/ chemicals have been used to improve bud break, especially in temperate regions. But there is no such comprehensive study on mulberry at whole plant / field level to induce a rapid and uniform bud break that can enhance foliage production.

Hence, there is a need of an effective method for inducing early, rapid and uniform bud break in mulberry plants. Also, there is a need of a method which can save water required for irrigation of mulberry plants.

Mulberry (Morus species) is traditionally best known for its predominant role in rearing silk worm (Bombyx mori L.) in sericulture industry. In addition, the crop is also known for its multifarious applications in medicinal/pharmaceutical and livestock industries. Recently, mulberry is being more recognized as an ideal system to produce rapid biomass to meet energy requirement, under the fast-changing global climate scenario, primarily because of its fast-growing nature. The tree can be routinely pruned to generate vegetative growth, that can serve as an important source for meeting ecological and energy goals (Cao et al. 2019).
Worldwide, India is the second leading producer of mulberry and silk. In India, most of the mulberry cultivation falls under arid or semi-arid conditions where the plants are routinely exposed to intermittent drought that adversely affects the biomass production. For rearing silkworm, the traditional practice is to harvest individual leaves or harvest the shoots. So, biomass /timely leaf production has been considered as one of the major constraints. One of the determinants of this multifactorial trait (biomass production) is the number of shoots (Vijayan et al. 2014), which in turn determined by the number of buds opened at a given time. Since mulberry cultivation practices involve frequent pruning, biomass/foliage production depends upon the efficiency of bud opening/break after pruning. Bud break and branch development in tree systems like mulberry is under the regulation of apical dominance, a phenomenon in plants wherein the control exerted by the shoot apex determines the overall growth and biomass production (Salemaa and Sievanen, 2002). Therefore, attempts are being made to overcome the apical dominance by chemical means. For example, 6-benzyl aminopurine (BAP) and Thidiazuron (TDZ) could induce rapid bud break in in-vitro studies (Tewari et al. 1999). Similarly, in different trees, growth regulators and diverse chemicals have been used to induce or to increase bud break, especially in temperate regions. However, there is no such studies in mulberry at whole plant/ field level to induce a rapid and uniform bud break that can enhance foliage/biomass production.
Hence, there is a need of an effective method for inducing early, rapid and uniform bud break so as to meet the timely biomass/ foliage demand from mulberry. Any approach to induce rapid bud break or a rapid biomass by saving irrigation water will be highly rewarding especially under water limited conditions. The present invention addresses this issue in mulberry.
Objective of the Invention:
The primary object of the present invention is to overcome the drawback associated with prior art to provide a new technical method of boosting growth in mulberry.
Another object of the present invention is to provide a method that can induce early, rapid and uniform budbreak in mulberry plants, which will not be critically limited by the regulation exerted by apical dominance.

Another object of the present invention is to provide a method that can induce an early and rapid foliage accumulation there by reducing the time needed forfoliage accumulation.

Another object of the present invention is to provide a method that can induce a bud break and accumulate foliage,irrespective of other environmental conditions, thereby increasing the number of harvests per year.

Another object of the present invention is to provide a method that can also save irrigation water required for mulberry plants.

Another object of the present invention is to provide a method that avoids use of chemicals/ growth regulators to achieve rapid bud break, as practiced in other perennial systems.

Another object of the present invention is to provide a method that avoids any ill effects caused by the chemical/s on the silkworm feeding, growth and development.

Summary of the Invention:
In an aspect of the Invention, there is provided an eco-friendly method of saving water and inducing rapid, early and uniform bud break and foliage growth in mulberry crop/s.
The method comprises following steps:
a) Inducing partial dehydration stress for a specific time duration of approximately 2 weeks at 40% soil field capacity prior to foliage harvest wherein the tissue water status/ relative water content (RWC) is maintained in the ranges of 65-70%;

b) Hydration treatment through irrigation to obtain the tissue water status above 90%.
Detailed Description of Drawings:
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of their scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:
Figure 1: This figure illustrates bud break (%) in mulberry plants at different days after dehydration, defoliation and rehydration. (Data represents the mean of six replications; error bar indicates standard error; ** indicates significance at p=0.01; Control-100% soil field capacity; Stress-40% soil field capacity).

Figure 2: illustrates representative image of bud break a) 10 days of defoliation and re-hydration b) 17 days after defoliation and re-hydration

Detailed Description:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
The Invention provides a method to induce rapid and early bud break and foliage growth by controlled irrigation under field conditions, without any chemical application. The method is easy and simple which have significant impact on mulberry biomass production and productivity.

The method facilitates induction of dehydration stress prior to foliage harvest and hydration through irrigation, post foliage harvest. The rate of bud opening and re-growth was significantly faster in these sets of plants compared to fully hydrated plants.

The method also saves irrigation water along with increasing the number of buds opened which in turn contribute for increased biomass (yield), thereby significantly contributing towards foliage production in mulberry, in an eco-friendly way.

The method overcomes the use of chemicals/ growth regulators to achieve rapid bud break, as practiced in other perennial systems. The method hence will not have any ill effects on the silkworm feeding, growth and development and also can save irrigation water.

In an embodiment, the method involves imposition of drought stress for a period of two weeks by withholding irrigation, followed by defoliation and re-watering.

In an embodiment, the eco-friendly method of saving water and inducing rapid, early and uniform bud break and foliage growth in mulberry crop/s comprises following steps:

a) Inducing partial dehydration stress for a specific time duration of approximately 2 weeks at 40% soil field capacity prior to foliage harvest wherein the tissue water status/ relative water content (RWC) is maintained in the ranges of 65-70%;

b) Hydration treatment through irrigation to obtain the tissue water status above 90%.

The early and rapid bud break was improved by approximately 34%. Approximately, 54% of the buds accumulated foliage in comparison with the plants grown under control condition showing 34% foliage. The method also saves irrigation water by about 50%.
The tissue water status is more crucial than number of days of stress imposition. It has been seen that in the other plant systems, vegetative tissues may not revive if water status drops below 50%. Therefore, it is essential to maintain the tissue water potential to revive the plant from stress and avoid them from reaching permanent wilting point (PWP).

The process provided by the present invention maintains the tissue water status/ relative water content (RWC) between 65-70% and for achieving the same, two weeks-controlled irrigation was performed at 40% soil field capacity.

To examine the effect of drought stress on bud break, the invention performs two different levels of soil water status (100 and 40% field capacities, FC) in potted mulberry plants by gravimetric approach. Drought stress was maintained for a period of two weeks, then irrigated to 100% FC, and the plants were then defoliated (all leaves harvested) to induce bud break.

As per the existing knowledge (as reported in earlier studies), slow or delayed bud opening in stressed plants was expected due to high levels of accumulation of inhibitors. From this context, it was expected that the control plants (maintained at 100% FC) would exhibit early bud break when compared to the stressed ones maintained at 40% FC.

However, an early and rapid bud break was observed in drought stressed plants when compared to non-stressed plants (100% FC), (Figure 1).

The results showed that while bud break was observed in 34% of the total buds in stressed plants, it was significantly lesser (p=0.01) in control plants (11%) 10 days post defoliation and re-watering (Figure 2). Bud break increased to 32 and 51% in control and stresses plants respectively at 20 days post defoliation and re-watering. At 30 days post defoliation and rewatering, while the stressed plants exhibited 54% bud break, the plants maintained at control conditions exhibited significantly lesser budbreak (34%, p=0.01) (Figure 2). The overall results showed that the stressed plants exhibited an early and rapid bud break compared to the control plants.

To demonstrate the breaking apical dominance, the invention performs two different levels of soil water status (100 and 40% field capacities, FC) in potted mulberry plants by gravimetric approach, using standard published protocol. Drought stress was maintained for a period of two weeks, the leaves were harvested before irrigating to 100% FC.

As per the existing knowledge (as reported in earlier studies), slow or delayed bud opening in stressed plants was expected due to high levels of accumulation of inhibitors. From this context, it was expected that the control plants (maintained at 100% FC) would exhibit early bud break when compared to the stressed ones maintained at 40% FC. However, an early and rapid bud break was observed in drought stressed plants when compared to non-stressed plants (100% FC), (Figure 1). The results showed that there was an early and rapid bud break (34%) using the present method in comparison with the plants grown under normal conditions (11%), at 10 days post treatment. At 30 days post treatment, 54% of the buds accumulated foliage in comparison with the plants grown under control condition (34%) (p=0.01).

Advantages:

1. The method induces an early and rapid foliage accumulation there by reducing the time needed for foliage accumulation.
2. The method increases the number of leaf harvest per year as it shortens the time needed for foliage accumulation
3. The method causes opening of a greater number of buds which significantly increases foliage yield, both underindividual leaf picking and shoot harvest methods.
4. The method saves irrigation water during every crop cycle as mulberry requires about one and a half totwo acre inches of water per irrigation once in 8-14 days.
,CLAIMS:We Claim:

1. An eco-friendly method of saving water and inducing rapid, early and uniform bud break and foliage growth in mulberry crop/s comprising the steps of:
a) Inducing partial dehydration stress for a specific time duration of approximately 2 weeks at 40% soil field capacity prior to foliage harvest wherein the tissue water status/ relative water content (RWC) is maintained in the ranges of 65-70%;

b) Hydration treatment through irrigation to obtain the tissue water status above 90%.

2. The method as claimed in claim 1, wherein early and rapid bud break was improved by approximately 34%.

3. The method as claimed in claim 1, wherein 54% of the buds accumulated foliage in comparison with the plants grown under control condition showing 34% foliage.

4. The method as claimed in claim 1, wherein the method saves irrigation water by about 50%.