Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Cloning And Characterization Of The Xa5 Disease Resistance Gene In Rice

Anjali S. Iyer¹ , Susan R. McCouch²

¹  Department of Plant Breeding and Genetics 240 Emerson Hall Cornell University Ithaca, NY 14853

²  Deptartment of Plant Breeding and Genetics 240 Emerson Hall Cornell University Ithaca, NY 14853

Rice, a staple food crop for millions and a model organism for plant molecular biology, is host to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight. Bacterial blight causes severe crop loss in South and Southeast Asia. Resistance to races of Xoo expressing the avirulence gene avrxa5 is mediated by the disease resistance (R) gene xa5, which has been mapped to the short arm of rice chromosome 5. xa5 is an unusual R gene in that it is recessive and race-specific. We have screened over 5000 individuals from an F2 population of an IR24 (susceptible) x IRBB5 (resistant) cross, and have narrowed the region containing xa5 to 5 candidate genes. Within this region are an ABC transporter, transcription factor IIA, two hypothetical proteins and a tRNA synthetase. RT-PCR analysis demonstated that all candidate genes are expressed in healthy, wounded and inoculated plants. Sequencing and further analysis of recombinant data will provide more information regarding the identity of this important gene.