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 seedyield in hybrid rice breeding programs. Exploitation of Elongated Uppermost Internode (eui) mutants in rice is a viable geneticstrategy to solve this problem. Present study was undertaken with an aim of characterizing the elongated uppermost internodemutants in rice germplasm and identifying the molecular markers linked to this trait. Ten IR 64 mutants possessing euimorphology were obtained from IRRI, Philippines. Mutants were grown under field conditions and observations on peduncleelongation 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 peduncleelongation rate (8 – 10 cm per day) than the wild type IR 64 (4 – 5 cm per day). At maturity, the eui mutants had longerpeduncles (44 – 52 cm) than the wild type (27.5 cm) which helped the mutants to bring out their panicles completely outside theboot leaf sheath. Marker genotyping of wild type IR 64 and mutants revealed the genetic association of two eui1 linked STSmarkers SAG01 and sMRF19 on chromosome 5 with eui trait. Genetic complementation analysis revealed the presence of novelmutation other than eui1 in the available mutant germplasm