Title: Linkage Drag: Implication for Plant Breeding Authors
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2010
Publication Date: February 22, 2010
Citation: Jia, Y., Costanzo, S., Lee, S., Lin, M.J., Jia, M.H. 2010. Linkage Drag: Implication for Plant Breeding. In: Proceedings of the 33rd Rice Technical Working Group Meeting. CDROM. Technical Abstract: Linkage drag is commonly observed in plant breeding, yet the molecular mechanisms controlling this is unclear. The Pi-ta gene, a single copy gene near the centromere region of chromosome 12, confers resistance to races of Magnaporthe oryzae that contain AVR-Pita. The Pi-ta gene in Tetep has been successfully transferred to several U.S. rice cultivars, Katy, Kaybonnet, Drew, Madison, Cybonnet, Ahrent, Spring, and Banks, by classical plant breeding. The Pi-ta gene is also found in IR64, the most widely grown rice cultivar in the world. Recently, we demonstrated that Pi-ta could produce 12 proteins (variants). Each Pi-ta variant may have the ability to recognize numerous races of blast fungus. In an effort to identify the minimal genomic region required for blast resistance, we discovered a large linkage block at Pi-ta in backcrossed progeny and elite cultivars. The presence of multiple resistance genes near Pi-ta may explain the observed durability of Pi-ta mediated resistance in the southern U.S. Genetic analysis of genes in global germplasm has revealed several novel resistance genes at the Pi-ta region. Genotyping of worldwide rice germplasm demonstrated that the Pi-ta linkage block is common in resistant accessions. The implications of linkage drag at the Pi-ta locus in disease resistance and crop productivity will be presented.