The identification and mapping of a tiller angle QTL on rice chromosome 9

Tiller angle is an important component of plant architecture in rice even though little is known of its mode of inheritance. A quantitative trait loci (QTL) analysis based on a set of recombinant inbred lines extracted from an indica x japonica cross identified a major effect locus (designated qTA-9a) on chromosome 9, which was expressed in two independent environments. The qTA-9a allele derived from the indica parent IR24 increased tiller angle. This QTL was validated in a set of chromosome segment substitution lines involving the same two parental lines. A high resolution genetic map was constructed from a large secondary F-2 population and anchored to the genomic sequence of rice. The QTL was narrowed to a 65-kb physical region, inclusive of eight putative genes. We have provided the basis for positional cloning of qTA-9a and have developed markers for a major tiller angle QTL.