QTL Mapping of Supernumerary Spikelets in Wheat.

Supernumerary Spikelets (SS) or branched spikes are one of the naturally occurring variants in wheat, where rachis nodes have more than one spikelet. Although this trait holds great prospects for increasing the number of grains in the spikes and ultimately increasing wheat yield, the detailed knowledge about molecular basis of spike branching in common wheat is still missing. In the present study, a population of 163 recombinant inbred lines (RIL) segregating for SS was used to map QTL associated with SS-related traits. The RIL, their parents, and seven checks were evaluated over six environments for penetrance of supernumerary spikelets (PSS), number of spikelets per spike (Sk), spike density (SD), number of spikelets per node (SkNd), number of nodes per spike with supernumerary spikelets (NdSS), number of extended rachilla per spike (NdR), and number of nodes with non SS (NdNonSS). A framework linkage map for this population was generated using a total of 939 DArT markers. The phenotypic data and the framework linkage map were used to identify and map QTL using composite interval mapping. QTL analysis suggested a polygenic inheritance for these traits with QTL identified on chromosome 2D, 5B, 6A, 6B and 7B. Most of these QTL were consistently identified for all SS-related traits across all environments. The major genomic region controlling these spike related traits could be the target for future studies aimed at cloning the underlying genes.