Parental Screening for QTL Pyramiding on Multiple-Abiotic Stress Tolerance under Irrigated Condition of Rice

Successful QTL pyramiding is a breeding technique to combine multiple tolerance genes from various donors into target rice cultivars as recipients without losing the recipients’ desirable traits. This study focuses on the abiotic stresses which are likely encountered by irrigated rice: submergence, anaerobic germination and salinity. Geographically, these stresses mainly occur in areas of South and Southeast Asia and African countries. Elite rice varieties from these regions include IR64, NSICRc238, Makassane and MS11 and therefore were chosen as recurrent parents. These were identified as the most advanced varieties with moderate to high grain-yield potential. Gene pyramiding is carried out through marker-assisted backcrossing (MABC), which involves simultaneous crossing of recurrent parents to donors to develop near isogenic lines (NILs), followed by intercrossing with each other. A parental survey using gene-specific markers was conducted to check for trait-specific alleles and to plan possible combinations. Results showed that MS11 and NSICRc238 have tolerant alleles for submergence (Sub1) and salinity (Saltol) respectively. Conversely, during phenotyping evaluation MS11 and Makassane showed tolerance to anaerobic germination, but all parents were susceptible to submergence and salinity screening. This infers that there may be other genes and QTLs governing these tolerances that have not yet uncovered. This study is useful for the development of multiple tolerance varieties, marker validation, and new allele mining. The end product of this QTL pyramiding project will be a small number of genotypes with multiple traits that would provide breeders with the opportunity to combine multiple trait tolerances in new rice varieties.