06-08-2013, 04:37 PM
Mapping of a bacterial blight resistant gene in Oryza using microsatellite markers
ABSTRACT
Rice (Oryza sativa L.) is an important crop whose productivity is affected by several biotic and abiotic stresses. Bacterial blight (BB) caused by Xanthomonas oryzae pv oryzae (Xoo) is one of the serious vascular wilt diseases prevalent throughout Asia especially under high input irrigated ecosystem. It is the major disease in India resulting in 75% yield losses. Resistance breeding is the most economical and environmentally safe approach for achieving yield stability. Oryza glaberrima harbours a reservoir of genes including BB that have allowed the species to survive and prosper in West Africa with minimal intervention. One accession of O. glaberrima (acc. 102600B) was identified as resistant to all seven races of Xoo pathotypes prevalent in northern states of India. Mapping of resistance in O. glaberrima was studied in BC1F2, BC2F2, BC2F3 and BC3F1 progenies of the cross involving Oryza sativa cv Pusa 44 and the O. glaberrima acc. 102600B using the most virulent Xoo pathotype. After genetic analysis of the segregating progenies it was observed that the BB resistance in O. glaberrima was conditioned by a single recessive gene. BSA and molecular mapping revealed two markers RM548 and RM593 at a distance of 1.7 and 1.1 cM respectively, to be associated with BB resistance. Since none of the earlier known Xa genes mapped on chromosome 5S, are effective against the Xoo pathotypes tested so this BB resistance gene identified and transferred from O. glaberrima is novel.