Molecular and genetic dissection of peduncle elongation in rice

Incomplete panicle exsertion in almost all the WA-based CMS lines is one of the major impediments in obtaining higher seed yield in hybrid rice breeding programs. Exploitation of Elongated Uppermost Internode (eui) mutants in rice is a viable genetic strategy to solve this problem. Present study was undertaken with an aim of characterizing the elongated uppermost internode mutants in rice germplasm and identifying the molecular markers linked to this trait. Ten IR 64 mutants possessing eui morphology were obtained from IRRI, Philippines. Mutants were grown under field conditions and observations on peduncle elongation rate, peduncle length, panicle exsertion and grain number were recorded. All the mutants excepting one mutant (D1027-2-3) possessed elongated peduncle when compared to wild type IR 64. The eui mutants exhibited accelerated peduncle elongation rate (8 – 10 cm per day) than the wild type IR 64 (4 – 5 cm per day). At maturity, the eui mutants had longer peduncles (44 – 52 cm) than the wild type (27.5 cm) which helped the mutants to bring out their panicles completely outside the boot leaf sheath. Marker genotyping of wild type IR 64 and mutants revealed the genetic association of two eui1 linked STS markers SAG01 and sMRF19 on chromosome 5 with eui trait. Genetic complementation analysis revealed the presence of novel mutation other than eui1 in the available mutant germplasm.