Panicle Length QTLs Identified Under Mild Drought and Low P Application in Rice (Oryza sativa L.)

This study is aiming for the identification of major quantitative trait loci (QTLs) for one of the yield related traits, panicle length and the related traits. Under mild drought and low phosphorus input conditions, the major traits related with panicle initiation and root establishment should be studied for high-yielding variety development. In this study, firstly four major QTLs for panicle length and yield-related traits identified on Chromosomes 1, 2, 9, and 11 were identified and studied under different water and P level conditions in two season experiments in a tropical region, Philippines. Total of 137 F_12:13 recombinant inbred lines (DT-RILs) derived from temperate indica or Tongil (Dasanbyeo) and japonica (TR22183) cross were genotyped by the 384-plex chipset using BeadXpress^TM system. The order of 233 out of the successfully called 236 polymorphic markers in the linkage map of DT-RILs was same as in the rice pseudomolecule. Panicle length QTL on Chromosomes 1 (pl1), 2 (pl2), and 11 (pl11) were closely linked to QTLs for grain number (gn1, gn2, and gn11), spikelet number (sn2 and sn11), and one hundred grain weight (hgw2) majorly under stressed conditions, while that of Chromosome 9 (pl9) was linked to QTLs for tiller number in early-mid stages (tn409 and tn609) and grain yield (gy59) of normal P conditions. RILs conferring Dasanbyeo-allele of pl2 and TR22183-allele of pl9 combination had the longest panicles, implying that a QTL pyramiding approach utilizing panicle length, early vegetative growth, and fertility under mild drought and limited P conditions will be effective.