Numerous studies have been conducted in rice to map quantitative trait loci (QTLs) associated with different agronomic traits. However, only a few of these studies have used interspecific mapping populations. Here, QTLs associated with tiller numbers, flowering time, plant height, and grain yield in an interspecific rice population were mapped. The population was evaluated under managed water-stressed (drought) and optimal (irrigated) environments. An interspecific rice population consisting of 254 BC2F5 lines derived from a cross between ‘CG14’ (Oryza glaberrima Steud.) as the donor and ‘WAB56-104’ (Oryza sativa L. ssp. japonica) as the recurrent parent was concurrently evaluated for three seasons (environments) under drought and irrigated environments. The study population was also genotyped with 136 simple sequence repeat (SSR) and 258 single nucleotide polymorphic (SNP) markers that were polymorphic between the two parents. The imposed drought reduced grain yield by approximately 56 and 72% in ‘CG14’ and ‘WAB56-104’ parents, respectively, and by 61% in the interspecific mapping population. Using inclusive composite interval mapping, a total of 44 QTLs distributed across all rice chromosomes except chromosome 10 were uncovered. Each QTL individually explained between 2.1 and 23.5% of the phenotypic variation and altogether accounted for 16.7 to 41.9% of the phenotypic and 38.8 to 73.8% of the genetic variation of a given trait. Five QTLs on chromosomes 2, 3 and 4 were identified both in the drought and irrigated environments and nine chromosomal regions harbored clusters of QTLs associated with two traits. The effect of the coincidental QTLs detected both under drought and irrigated environments was highly variable, with two QTLs showing the same effect in both water regimes and three showing from 3- to 16-fold greater effect under drought than irrigation environments. Results from this study may provide useful information to rice researchers working towards delivering improved drought tolerant varieties.

Keywords: Mapping, Oryza glaberrima, Oryza sativa, quantitative trait locus (QTL), drought, phenotypic variation, coincidental QTLs.