Pyramiding QTLs Using Multiparental Advanced Generation Introgression Lines Enhances Salinity Tolerance in Rice

Rice is a major cereal that nourishes more than half of the global population. But rice lands are under threat from soil salinity leading to reduced productivity. Salinity stress tolerance is challenging due to the multigenic trait and complex tolerance mechanisms. QTL pyramiding is one of the efficient approaches to stack desired genes and QTLs from multiple donors. This study developed three populations using multiple salt-tolerant introgression lines (ILs) to accumulate beneficial alleles/QTLs and identify improved salt-tolerant breeding lines. To accumulate the salt-tolerant alleles from salt-tolerant donors, we used salt-tolerant ILs of Pokkali and Nona Bokra in the CL151 background (CLPK683 and CLPK757) and Jupiter background (JN100 and JN520), respectively. The QTLs for shoot Na + and K + content , qNa2.2 , qK2.1, and qK2.2, from JN100 and qK4.1 and qK8.1 from JN520 were targeted using the molecular markers linked to these QTLs. Both phenotypic and genotypic selection methods were employed to advance the populations. The F 5 populations of each cross were finally evaluated for seedling-stage salt tolerance. The visual salt injury score (SIS) and shoot Na + and K + concentration in selected lines indicated salt tolerance higher than the IL parents. The targeted QTLs were detected in most salt-tolerant lines. The salt-tolerant breeding lines identified in this study constitute a valuable resource for investigating the physiological and molecular basis of salt tolerance and identifying superior alleles of salt-tolerance genes for use in breeding programs.