| dc.description.abstract | Peanut production is increasingly challenged by frequent and severe drought events worldwide. Rather than relying on costly irrigation systems, cultivating drought-tolerant cultivars offers a more sustainable approach for agricultural resilience. While some drought-tolerant genotypes have been previously identified, a deeper understanding of the mechanisms behind drought tolerance is necessary to support breeding efforts. Effective drought tolerance strategies in peanuts include enhanced biological nitrogen fixation (BNF), inoculation with rhizobia with high 1-Aminocyclopropane-1-carboxylate (ACC) deaminase activity, partial stomatal closure to reduce water loss, and maintenance of higher stomatal conductance under drought through growing deeper root systems. From 2019 to 2022, a series of field and greenhouse experiments were conducted to explore these drought tolerance mechanisms. Our findings indicate that increased BNF in a specific number of drought-tolerant cultivars contributes to higher yields under drought with concomitant maintenance of higher leaf water status, as indicated by relative water content, being critical for optimal BNF performance. While the inoculation effect of strains with ACC deaminase on drought tolerance was not significant, peanut plants inoculated with strains carrying acdS genes showed improvements in root biomass and BNF under well-watered and drought conditions. Significant genotypic differences in root morphology traits, such as root angle, number of root tips, and average root diameter, were observed in field experiments under irrigated and rainfed conditions. Drought tolerant cultivars, AU-NPL 17 and AU18-35, exhibited steeper root angles supporting other evidence that classified these cultivars as water-spender cultivars. In the study of detection of drought tolerance related quantitative trait loci (QTLs) from an F2 population, significant reductions were observed in yield, shoot biomass, harvest index (HI), photosynthesis, stomatal conductance, and C13 in parent and F1 populations in 2021 under drought. However, AP-3 exhibited superior performance in the single plant setting, demonstrating reduced sensitivity to drought stress. The linkage map was constructed with 471 markers on 20LGs covering 1403.33cM and with an average inter-marker distance of 2.98cM. A total of 27 QTLs associated to physiological traits (pod count, shoot, HI, C13, N15, photosynthesis, stomatal conductance and SPAD) related to drought tolerance were detected in F2 experiment. These identified QTLs could aid in better characterizing drought-tolerant genomic regions and improve marker-assisted selection for these traits in peanut breeding programs for drought-tolerant genotypes. | en_US |
