Validation of QTLs in Bangladeshi rice landrace Horkuch responsible for salt tolerance in seedling stage and maturation

The upsurge in global temperatures and the increasing threat of salinity are adversely affecting rice productivity in the southern coastal lands of Bangladesh. A Bangladeshi rice landrace Horkuch, adapted to these saline conditions, has long been cultivated by farmers in this region. To understand the trend and heritability of its tolerance traits, a reciprocal population of Horkuch with the high-yielding sensitive rice IR29 was generated for mapping of quantitative trait loci (QTLs) at both seedling and reproductive stages in an F-2:3 strategy using double-digest restriction associated DNA. We found 29 QTLs and some QTL clusters containing survival and yield-related QTLs showing pleiotropic effects over some phenotypes. We advanced the generation up to F-5 to obtain homozygosity and our current work is aimed at confirming these mapped QTLs at F-5 by salt stress physiological tests at both stages as well as DNA markers linked to these QTLs. We confirmed SES QTL (survival of seedling under stress) associated with SSR marker RM25789 and two QTL clusters at chromosome 10 and 11 associated with RM26964 and RM27027, respectively. One cluster harbored yield-related filled grain number, filled grain weight, total grain number, harvest index, ionic balance and transpiration-related total sodium, total potassium and stomatal conductance QTLs. The other cluster contained total grain weight, filled grain weight and seedling root relative water content QTLs. We identified some individuals based on their physiological performance under stress as well as the presence of QTLs associated with some SSR markers that can be used for breeding and production of highly salt-tolerant cultivars with high yield.