Title: Identification of rice blast resistant gene Pi-z(t) in NSGC using DNA markers and pathogenicity assays Authors
Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 5, 2010
Publication Date: August 12, 2010
Citation: Roy-Chowdhury, M., Jia, Y., Jia, M.H., Jackson, A.K., Fjellstrom, R.G., Cartwright, R.D. 2010. Identification of rice blast resistant gene Pi-z(t) in NSGC using DNA markers and pathogenicity assays [abstract]. 5th International Rice Blast Conference, August 12-14, 2010, Little Rock, Arkansas. Poster Abstract IV-CP-51. Technical Abstract: Rice blast disease, caused by the fungus Magnaporthe oryzae (formerly Magnaporthe grisea) is a major fungal disease threatening rice production worldwide. Genetic resistance in rice to M. oryzae typically belongs to a classic gene-for-gene system where a resistance (R) gene is effective in preventing infections by races of M. oryzae containing the corresponding avirulence (AVR) gene. Presently the use of R genes is the most economical and environmentally benign method to manage blast disease. Thus far, more than 80 race-specific R genes to M. oryzae have been identified and some of them have been molecularly cloned and tagged for marker-assisted selection (MAS). Among the tagged blast R genes, the Pi-z(t) gene initially identified by Kiyosawa has been effectively introgressed into numerous rice cultivars around the globe to prevent infection by a wide range of races of the rice blast pathogen. In the U.S., Pi-z(t) was first identified in the medium grain cultivar ‘Zenith’. This gene has been shown to confer resistance to five U.S. races of blast, IH-1, IG-1, IC-17, IE-1 and IE-1k, and susceptibility to two races, IB49 and IB33, respectively. The objective of this present study was to characterize Pi-z(t) in 131 rice germplasm accessions selected from the NSGC using DNA markers and pathogenicity assays. Four simple sequence repeat (SSR) markers (RM527, AP4791, AP5659-1, AP5659-5) closely linked to Pi-z(t) were used to predict Pi-z(t) in rice germplasm and the results were verified using pathogenicity assays with an avirulent strain (IE1k) and two virulent races, IB33 and IB49. The presence of the Pi-z(t) gene in 98 germplasm accessions out of 131 was verified using both SSR markers and pathogenicity assays. The remaining 33 germplasm accessions containing unexpected SSR alleles were found to be different in their responses to blast races, IB33, IEIk and IB49, suggesting the presence of additional Pi-z(t) independent R gene(s). These characterized germplasms should be useful for genetic studies and marker-assisted breeding for improving blast resistance worldwide. References: 1. Kiyosawa S.1967. The inheritance of resistance of the Zenith type varieties of rice to the blast fungus. Jap J Breed 17:99-107. 2. Fjellstrom R, McClung AM, Shank AR. 2006. SSR markers closely linked to the Pi-z locus are useful for selection of blast resistance in a broad array of rice germplasm. Mol Breed 17:149–157. 3. Valent B, Farrall L, Chumley FG .1991. Magnaporthe grisea genes for pathogenicity and virulence identified through a series of backcrosses. Genetics 127:87–101.