QUANTITATIVE TRAIT LOCI MAPPING OF SALINITY TOLERANCE IN GENETICALLY DIVERSE RICE POPULATIONS

Abstract

Background: Salinity stress is one of the major environmental constraints limiting rice production in the world, especially in coastal and irrigated agricultural areas. Excess accumulation of salt disturbs ion balance, decreases water absorption and damages photosynthesis and ultimately decreases plant growth and grain yield. Therefore, identification of salt-tolerant genetic loci is a prerequisite for the development of climate-resilient rice cultivars.
Objective: The aim of the present study was to identify and characterize quantitative trait loci (QTLs) for salinity tolerance in genetically diverse rice populations.

Methods: Recombinant inbred line and diverse rice genotypic mapping populations were generated and screened under controlled saline stress conditions. Phenotypic traits, including survival rate, shoot biomass, chlorophyll content, and Na+/K+ ion ratio were measured. Genotyping was done using SNP and SSR molecular markers and linkage mapping and QTL association analysis was carried out.

Findings: We identified several major QTLs for salinity tolerance including the major Saltol locus on chromosome 1 with a LOD score of 5.8, explaining around 32% of the phenotypic variance. Salt tolerant genotypes had 40% higher survival rates, better Na+ exclusion and improved ion homeostasis than sensitive lines. Strong marker-trait associations were found for seedling vigor and stress tolerance.

Conclusions: Our QTL mapping has provided useful genomic resources for marker-assisted breeding and development of high yield salt-tolerant rice cultivars for saline agricultural environments.