Abstract:
A recombinant inbred line (RIL) population was previously developed with two high yielding rice varieties, At354,
a salt tolerant parent and Bg352, a salt susceptible parent aiming at identifying salinity tolerant QTLs together with
varietal development. In this study we used 100 F5 RILs of At354 x Bg352 to characterize the population and map
genes for salt tolerance. Nine morpho-physiological parameters related to salinity tolerance were assessed under
hydroponics supplemented with 100 mM NaCl concentration (12 dS/m). Frequency distributions of these 9 morpho physiological traits, standard evaluation score, salinity survival index, shoot length, root length, shoot dry weight,
root dry weight, shoot Na+
concentration, shoot K+
concentration and shoot Na+
/K+
ratio indicated the broad
spectrum of genetic variability in the RIL population under salinity stress while correlation coefficients also were
significant with each other. Broad sense heritability also proved that the population was suitable for the gene
mapping for salinity tolerance. Composite Interval mapping revealed 6 QTLs distributed in chromosome 1 and 4
namely, qSSI1, qSL1, qSNK1, qSL4, qSNK4 and qSSI4, explaining 10.8%, 10%, 8.9%, 15%, 11% and 16% of the
phenotypic variations respectively. In all QTLs At354 allele contributed in favour of salinity tolerance. However,
closer flanking markers could not be detected due to the low rate of polymorphism in SSR markers which generated
low density molecular map. Therefore, further studies incorporating high throughput marker technologies would be
necessary for detecting QTLs with narrow marker intervals.
