QUANTITATIVE TRAIT LOCUS ANALYSIS FOR RICE PANICLE AND GRAIN CHARACTERISTICS

The development of molecular genetic maps has accelerated the identifi cation and mapping of genomic regions controlling quantitative charact ers, referred to as quantitative trait loci or QTLs. A molecular map d erived from an F-2 population of a tropical japonica x indica dress (L abelle/Black Gora) consisted of 116 restriction fragment length polymo rphism (RFLP) markers. Composite interval mapping was used to identify the QTLs controlling six panicle and grain characteristics. Two QTLs were identified for panicle size at LOD > 3.0, with one on chromosome 3 accounting for 16% of the phenotypic variation. Four loci controllin g spikelet fertility accounted for 23% of the phenotypic variation. Se ven, four, three and two QTLs were detected for grain length, breadth, shape and weight, respectively, with the most prominent QTLs being on chromosomes 3, 4, and 7. Grain shape, measured as the ratio of length to breadth, was mostly controlled by loci on chromosomes 3 and 7 that coincided with the most important QTLs identified for length and brea dth, respectively. A model including three loci accounted for 45% of t he phenotypic variation for this trait. The identification of economic ally important QTLs will be useful in breeding for improved grain char acteristics.