RESPONSE OF MAIZE (Zea mays L.) TO EXOGENOUS APPLICATION OF SALICYLIC ACID UNDER LIMITED WATER AVAILABILITY

Abstract

Premise of the research- Maize occupies a reputed rank among the top cereals of the world. Drought stress alters various physiological and biochemical processes going on in the maize plants resulting into various irreparable damages to various organelles of the plant cells which ultimately causes a significant loss of yields. Various plant growth regulators are reported to have positive roles in the drought stress amelioration. However, exogenous application of SA on the maize (Zea mays L.) hybrids has been argued to have role in abiotic stress amelioration but the studies supporting the notion are scant. Methodology- Laboratory, wire-house, lysimeters and filed experiments were conducted for this study. Polyethylene glycol (PEG8000) induced water deficit conditions were imposed on eight spring maize hybrids selected from different sources for screening at germination stage. Seeds were sown in the Petri plates were applied with PEG8000 @ -0.6MPa. In the wire-house conditions same eight maize hybrids were screened at seedling stages. In this study two drought stress conditions (100% FC and 60% FC) were imposed on the maize hybrids. From these experiments two maize hybrids were selected as drought tolerant (DK-6525) and drought sensitive (NK-8711) as drought sensitive one. These two maize hybrids were then used for the dose optimization study for seed priming and foliar spray of salicylic acid (SA). In the dose optimization for seed priming with SA five treatments (No priming, hydro-priming, priming with SA @ 50 mg L-1, 100 mg L-1 and 150 mg L-1) were applied to the both maize hybrids in the normal as well as water deficit conditions. From the above study seed priming with mg L-1 gave better results. In the same way for the dose optimization of foliar spray the same experimentation was repeated as was in priming experiment. There were two moisture stress levels were selected in which no water stress conditions and water stress conditions were imposed. SA was applied at the rate of no spray, water spray, SA @ 50, 100 and 150 mg L-1. SA at the rate of 100 mg L-1 was found best of all. In the next experiment, optimum method of SA application was found, in this experiment plant were sown till their maturity. There were nine treatments in this experiment: (1) No Priming and No Spray (2) Hydro-priming (3) Priming with optimum dose of SA selected from the previous experiment (4) Water spray at vegetative growth stage (5) Foliar spray of SA at the vegetative growth stage (6) Water spray at reproductive stage (7) Foliar spray of SA at the reproductive stage (8) priming along with foliar at vegetative stage and (9) priming with SA along with foliar spray with SA at the reproductive stage. Foliar spray of SA @ 100 mg L-1 at vegetative growth stage was found more viable method. Further, another experiment was conducted to find the best time of SA application in this experiment following treatments: (1) no spray at all (2) spray with distilled water and (3) foliar spray of SA at the rate of 100 mg L-1 were applied in the four moisture stress conditions: (1) no moisture stress which was considered as control (2) moisture stress at vegetative growth stage (3) moisture stress at reproductive stage and (4) moisture stress at vegetative and reproductive stages both). Vegetative growth stage was found more responsive towards the foliar spray of SA @ 100 mg L-1. After that the above mentioned studies were checked in the field conditions for two consecutive growing seasons. In the field conditions water stress was imposed by skipping the irrigations at the vegetative growth stages, instead of applying irrigation SA was sprayed at the above mentioned rate. Control conditions were those where no spray was done at all. Agronomic parameters recorded suggested that SA was found effective in ameliorating the negative impacts of drought and ultimately an increase in the yields was observed. The same trends were observed in the next year filed experiment Conclusion- Maize hybrids were suggested to screen for their drought tolerance potential for precision agriculture and SA spray can compensate the losses water absence by improving drought tolerance and enhancement of yields.