Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 1, 2004
Publication Date: November 15, 2005
Citation: Fjellstrom, R.G., Shank, R.A., McClung, A.M., Jodari, F. 2004. Genetic mapping of microsatellite (SSR) markers linked to the rice Pi-i blast resistance gene [abstract]. 2nd International Symposium of Rice Functional Genomics. p. 98.
Rice blast is a major fungus disease threat to rice production throughout the world. Genes conferring resistance to blast are a valuable and environmentally-friendly means to minimize crop losses from this serious disease. The Pi-i blast resistance gene has been utilized worldwide as a source of disease resistance, and has been indirectly mapped onto rice chromosome 9. Inukai et al. (1994) found that Pi-i mapped 6.2 cM from Pi-3; Jeon et al. (2003) mapped Pi-5 onto rice chromosome 9 and also reported that the Pi-3 and Pi-5 have identical genomic regions; and Yi et al. (2004) reported that development of unique dominant markers for the Pi-5 gene that were only present in advanced monogenic rice lines carrying the Pi-i, Pi-3, and Pi-5 genes and in cultivars historically recognized as carrying the Pi-i gene. Herein, we report the direct linkage analysis of the Pi-i gene in USA germplasm using co-dominant microsatellite (SSR) markers mapping near the Pi-5 locus identified by Jeon et al. Pi-i mapping was analyzed in two genetic crosses made between the cultivar L-205, carrying the Pi-i gene, and two breeding lines lacking Pi-i. Progeny from these crosses segregating for the Pi-i gene were screened for resistance to blast race IH-1. Results indicate that the Pi-i blast resistance factor conferring resistance to race IH-1 maps to the same region as the PI-5 gene, supporting the findings of Jeon et al. and Yi et al. The presence of several marker haploytpes among cultivars reported to have the Pi-i gene and IH-1 resistance indicates that this gene region is highly variable and that numerous resistance alleles can be found at the Pi-i/Pi-3/Pi-5 locus. The i gene can readily be used for marker assisted selection of this blast resistance gene.