Genetic Components and QTL Analysis for Salinity Tolerance in Rice (Oryza sativa L.) at the Reproductive Stage

Genetic components and combining ability estimates of rice (Oryza sativa L.) at reproductive stage under salinity stress were investigated using a seven-parent full-diallel cross analysis. Sadri (IRGC Acc. No. 32329), an Iranian genotype, was found as the best general combiner for grain yield under salinity stress. The F₁ hybrids, Sadri×CSR28 and Sadri×FL478 (IR669646-3R-178-1-1) got the highest grain yield of 55.68 and 54.29 g per plant, respectively. Estimate of genetic parameters of the 14 characters at reproductive stage revealed that both additive and dominance effects were significant for days to flowering, plant height, panicle length, number of sterile spikelets, spikelet fertility, 1000-grain weight, Na⁺ uptake, K⁺ uptake and K-Na ratio. For number of panicles, straw dry weight, number of fertile spikelets and grain yield, only dominance effects were significant.

The F₂ progenies (232 nos.) derived from cross between Sadri and FL478, were phenotyped for salinity stress at reproductive stage to identify the associated robust QTL regions. Phenotyping was conducted at IRRI in the artificially salinized field stress condition of electrical conductivity (EC) 6-8 dSm^-1. A genetic linkage map was constructed using 123 microsatellite markers and identified QTLs through composite interval mapping using QGENE software. Total 35 QTLs were detected for yield and yield components under salinity stress at reproductive stage. QTL clusters on chromosome 2, 4 and 6 in this study are going to be fine mapped. Robust fine mapped QTLs will be helpful for identification of closely linked markers and molecular breeding for salinity tolerance in rice.