Association mapping of drought tolerance and agronomic traits in rice (Oryza sativa L.) landraces

Abstract

Background Asian cultivars were predominantly represented in global rice panel selected for sequencing and to identify novel alleles for drought tolerance. Diverse genetic resources adapted to Indian subcontinent were not represented much in spite harboring useful alleles that could improve agronomic traits, stress resilience and productivity. These rice accessions are valuable genetic resource in developing rice varieties suited to different rice ecosystem that experiences varying drought stress level, and at different crop stages. A core collection of rice germplasm adapted to Southwestern Indian peninsular genotyped using SSR markers and characterized by contrasting water regimes to associate genomic regions for physiological, root traits and yield related traits. Genotyping-By-Sequencing of selected accessions within the diverse panel revealed haplotype variation in genic content within genomic regions mapped for physiological, morphological and root traits. Results Diverse rice panel (99 accessions) were evaluated in field and measurements on plant physiological, root traits and yield related traits were made over five different seasons experiencing varying drought stress intensity at different crop stages. Traits like chlorophyll stability index, leaf rolling, days to 50% flowering, chlorophyll content, root volume and root biomass were identified as best predictors of grain yield under stress. Association mapping revealed genetic variation among accessions and revealed 14 genomic targets associated with different physiological, root and plant production traits. Certain accessions were found to have beneficial allele to improve traits, plant height, root length and spikelet fertility, that contribute to the grain yield under stress. Genomic characterization of eleven accessions revealed haplotype variation within key genomic targets on chromosomes 1, 4, 6 and 11 for potential use as molecular markers to combine drought avoidance and tolerance traits. Genes mined within the genomic QTL intervals identified were prioritized based on tissue specific expression level in publicly available rice transcriptome data. Conclusion The genetic and genomic resources identified will enable combining traits with agronomic value to optimize yield under stress and hasten trait introgression into elite cultivars. Alleles associated with plant height, specific leaf area, root length from PTB8 and spikelet fertility and grain weight from PTB26 can be harnessed in future rice breeding program.

Growth and Nutritional Quality of Lemnaceae Viewed Comparatively in an Ecological and Evolutionary Context

“…Other examples for terrestrial plants with high growth rates are annuals and biennials that also complete their life cycle in a relatively short period of time and grow where they can maintain access to water. These species may employ evasive approaches to keep internal water content high, e.g., by performing osmotic adjustment to maintain metabolic activity [48] and increasing their investment in water-mining root structures [49] (Table 1). These terrestrial plants do not put the brakes on growth until water becomes scarce, and then switch to seed production-reminiscent of the production of vegetative storage forms (turions) in Lemnaceae.…”

Intraspecific Variation for Leaf Physiological and Root Morphological Adaptation to Drought Stress in Alfalfa (Medicago sativa L.)

“…The outbreeding mating system and its ploidy level made conventional breeding challenging tasks in improving various agronomic traits in alfalfa ( Zhou et al, 2011 ) was reviewed recently by Stacy et al (2018) . Crop wild relatives are viewed as novel genetic resources and identified key traits to improve stress resilience in other major legume species ( Manavalan et al, 2015 ; Prince et al, 2015b , 2020 ; Beena et al, 2021 ). In this study, different alfalfa genotypes adapted to a mild desert climate (PI478573) and a cold region with a prolonged winter (PI502521) along with cultivar Bulldog805 were evaluated to identify beneficial leaf and root traits in alfalfa to increase productivity under water limitation.…”

Favorable QTLs from Oryza longistaminata improve rice drought resistance

“…is the most economically important crop, and a staple food for more than half of the global population [ 1 ]. Rice yield is frequently limited by several abiotic factors such as cold, flood, and drought caused by climate change [ 2 ]. Climate related diverse abiotic stresses are the principal sources of risk and uncertainties in agriculture and caused wide fluctuations in agricultural output [ 3 ].…”