ABSTRACT
Drought stress is the main growth-limiting factor in pigeon pea production. Plant growth-promoting bacteria (PGPB) induce abiotic stress tolerance in several plants. However, the physiological and molecular changes with PGPB priming are not well understood in pigeon pea. The present study explored the potential of Firmibacteria (Bacillus azotoformans MTCC2953, Bacillus aryabhattai KSBN2K7, and Paenibacillus stellifer M3T4B6) to induce stress tolerance in pigeon pea under pot culture condition. Different physiological and biochemical parameters, including osmolytes, stress enzymes, and antioxidants, were evaluated under two stress conditions (50% and 25% field capacity) and an unstressed condition in pigeon pea. Under moisture stress conditions significant differences were observed in physiological and biochemical parameters between firmibacteria inoculated and control plants.The quantitative real-time polymerase chain reaction was performed to study the bacterial inoculation mediated expression of proline and drought-responsive genes in enhancing the drought tolerance in pigeon pea. Results showed that the inoculation of Bacillus aryabhattai upregulated the expression of drought-responsive genes (C. cajan_29830 and C. cajan_33874) and downregulated the expression of the proline gene by inducing the drought stress tolerance in inoculated plants compared with the uninoculated control plants. Therefore, Bacillus aryabhattai may be recommended for inducing drought stress tolerance and increasing the growth of pigeon pea under moisture stress conditions after field evaluation.
ABSTRACT
Drought is a serious threat to the farming community, biasing the crop productivity in arid and semi-arid regions of the world. Drought adversely affects seed germination, plant growth, and development via non-normal physiological processes. Plants generally acclimatize to drought stress through various tolerance mechanisms, but the changes in global climate and modern agricultural systems have further worsened the crop productivity. In order to increase the production and productivity, several strategies such as the breeding of tolerant varieties and exogenous application of growth regulators, osmoprotectants, and plant mineral nutrients are followed to mitigate the effects of drought stress. Nevertheless, the complex nature of drought stress makes these strategies ineffective in benefiting the farming community. Seed priming is an alternative, low-cost, and feasible technique, which can improve drought stress tolerance through enhanced and advanced seed germination. Primed seeds can retain the memory of previous stress and enable protection against oxidative stress through earlier activation of the cellular defense mechanism, reduced imbibition time, upsurge of germination promoters, and osmotic regulation. However, a better understanding of the metabolic events during the priming treatment is needed to use this technology in a more efficient way. Interestingly, the review highlights the morphological, physiological, biochemical, and molecular responses of seed priming for enhancing the drought tolerance in crop plants. Furthermore, the challenges and opportunities associated with various priming methods are also addressed side-by-side to enable the use of this simple and cost-efficient technique in a more efficient manner.
