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Rice alone consumes more than half of all irrigation water. Hence there is a pressing need to conserve irrigation water, which can only be accomplished by cultivating rice with less water. This involves increasing plant characteristics which makes it easier for adaptation of rice to produce more with less water. Given the importance of enhancing abiotic stress adaption, a complete and coordinated approach must be developed and implemented. Trait-based breeding is the most cutting- edge approach for rice plant genetic development. This chapter details the various approaches conducted for capturing the Acquired tolerance traits (ATTs), under different stresses as well as their validation using 18 rice germplasm accessions.
Plants deal with stress by developing adaptive mechanisms that are grouped into two categories: constitutive and acquired traits (Xin, 1998; Sheshshayee et al., 2018). Acquired tolerance traits (ATTs) are characterized as mechanisms that are conspicuously up regulated when plants are exposed to milder stress, and these mechanisms would then give plants with higher degrees of tolerance when the stress levels subsequently become more severe. These ATTs are mainly related to maintenance of redox balance by scavenging reactive oxygen species (ROS), maintenance of protein tertiary structure through folding and unfolding, protection to membranes through chaperons, cellular ionic homeostasis etc. Under stress excess electrons are transferred to oxygen reduction (Jastroch' et al., 2010; Jin et al., 2013), resulting in the production of reactive oxygen species (ROS). Plants have also evolved effective strategies by preventing the accumulation of free radicals either by restricting the production or by scavenging them (Poljšak et al., 2013; Khan et al., 2018). Therefore, managing ROS levels appears to be the most crucial strategy which is often "induced" when the stress levels are milder (Sofo et al., 2015; Pour-Benab et al., 2019). Thus, determining the levels of acquired tolerance is generally performed at a young seedling stage by providing a mild "induction" treatment (Srikanthbabu et al., 2002; Senthil-kumar et al., 2003). The main aim of the present study was to understand the mechanism underlying acquired tolerance traits and to analyze the response of plant to exogenous metabolite treatments against ROS production under different abiotic stresses.
KEYWORDS: Reactive oxygen species, acquired tolerance, Drought stress, abiotic stress tolerance, Rice (Oryza sativa).
