Induction of Acquired Tolerance Through Gradual Progression of Drought Is the Key for Maintenance of Spikelet Fertility and Yield in Rice Under Semi-irrigated Aerobic Conditions

Abstract

Plants have evolved several adaptive mechanisms to cope with water-limited conditions. While most of them are through constitutive traits, certain “acquired tolerance” traits also provide significant improvement in drought adaptation. Most abiotic stresses, especially drought, show a gradual progression of stress and hence provide an opportunity to upregulate specific protective mechanisms collectively referred to as “acquired tolerance” traits. Here, we demonstrate a significant genetic variability in acquired tolerance traits among rice germplasm accessions after standardizing a novel gradual stress progress protocol. Two contrasting genotypes, BPT 5204 (drought susceptible) and AC 39000 (tolerant), were used to standardize methodology for capturing acquired tolerance traits at seedling phase. Seedlings exposed to gradual progression of stress showed higher recovery with low free radical accumulation in both the genotypes compared to rapid stress. Further, the gradual stress progression protocol was used to examine the role of acquired tolerance at flowering phase using a set of 17 diverse rice genotypes. Significant diversity in free radical production and scavenging was observed among these genotypes. Association of these parameters with yield attributes showed that genotypes that managed free radical levels in cells were able to maintain high spikelet fertility and hence yield under stress. This study, besides emphasizing the importance of acquired tolerance, explains a high throughput phenotyping approach that significantly overcomes methodological constraints in assessing genetic variability in this important drought adaptive mechanism.

Comprehensive analysis of physiological and metabolomic responses to drought reveals specific modulation of acquired tolerance mechanisms in rice

“…The ability of a genotype to sustain growth under WL conditions depends on specific ATTs besides integral traits such as roots and water use efficiency (Lekshmy et al, 2021; Sreeman et al, 2018). Since our hypothesis was around the fact that milder stress “induces” certain protective mechanisms (Lekshmy et al, 2021), we looked for the TRI metabolites that help maintain better and balanced metabolism under stress conditions.…”

“…Maintenance of SF is an extremely important prerequisite for achieving higher yields and harnessing water‐saving practices in rice cultivation (Lekshmy et al, 2021; Raju et al, 2014). With several metabolites displaying differential expression between WL and WW conditions and between tolerant and sensitive genotypes, we examined the performance of the selected genotypes under MDEs.…”

“…The ability of a genotype to sustain growth under WL conditions depends on specific ATTs besides integral traits such as roots and water use efficiency (Lekshmy et al, 2021;Sreeman et al, 2018).…”

“…This witnessed increased attempts to improve certain specific physiological traits such as root traits, WUE, and forth (for review, see Sreeman et al, 2018). Although these “constitutive” traits have relevance, harnessing the ability of a plant to respond to stress at the cellular level through the expression of specific traits would be equally crucial for a comprehensive improvement in drought adaptation to sustain productivity under water‐limiting conditions (Lekshmy et al, 2021; Raju et al, 2014; Zhang et al, 2021).…”

Integrated Analysis of Osmotic Stress and Infrared Thermal Imaging for the Selection of Resilient Rice Under Water Scarcity

“…The standard evaluation scoring system (SES) was used as a primary criterion to screen rice genotypes for water stress tolerance or susceptibility ( International Rice Research Institute [IRRI], 2014 ). Several morpho-physiological parameters, for example, root and shoot lengths, fresh and dry weights, relative water content, membrane stability index (MSI), chlorophyll, and proline content are being used for screening the genotypes for water stress tolerance ( Lekshmy et al, 2021 ). A complex antioxidant system including both enzymatic and non-enzymatic antioxidants is a protection mechanism adopted by plants to avoid the damaging effects of ROS ( Hasanuzzaman et al, 2020 ).…”