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Location: Dale Bumpers National Rice Research Center

Title: Characterization of Pi-ta Blast resistance gene in an international rice core collection

item Wang, Xueyan
item Fjellstrom, Robert
item Jia, Yulin
item Yan, Wengui
item Jia, Melissa
item Scheffler, Brian
item Wu, Dianxing
item Shu, Qingyao
item Mcclung, Anna
item Mcclung, Anna

Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2009
Publication Date: 10/1/2010
Citation: Wang, X., Fjellstrom, R.G., Jia, Y., Yan, W., Jia, M.H., Scheffler, B.E., Wu, D., Shu, Q., McClung, A.M. 2010. Characterization of Pi-ta Blast resistance gene in an international rice core collection. Plant Breeding. 129(5):491-501.

Interpretive Summary: Identification and characterization of blast resistance (R) genes are critical tasks to determine the presence of new virulent pathogen races. R genes to rice pathogens are predicted to be distributed among rice germplasm worldwide. The major blast R gene Pi-ta has been effectively deployed to control disease caused by all major races of the blast pathogen in the Southern US since 1990. However a virulent pathogen race (IE-1k) overcoming Pi-ta was found and reported to cause significant crop losses in several commercial rice fields. In the present study, a subset consisting of 193 world accessions was assembled to identify rice germplasm that contain the Pi-ta gene and germplasm that contain R gene to the race IE-1k. The Pi-ta gene was initially identified in 159 genetically diverse germplasm using an indel marker for Pi-ta. The intron and carboxyl terminus of the Pi-ta gene were also sequenced in the 193 accessions to verify the existence of the Pi-ta gene. The results showed that all 159 accessions contain the Pi-ta gene and a single amino acid alanine at the 918 position of the Pi-ta protein was confirmed to determine resistance specificity. In addition, a new single nucleotide polymorphism (SNP) in the intron region of the Pi-ta gene was identified to correlate with resistance. Ultimately, 83 accessions were identified to contain resistance genes not found in the US cultivars and which conferred resistance to race IE-1k. These accessions are useful as the resistance donors for rice improvement in the southern US.

Technical Abstract: The Pi-ta gene in rice prevents infections by races of Magnaporthe oryzae containing AVR-Pita. In the present study, 1,790 accessions were characterized for Pi-ta, and the Pi-ta independent resistance genes using marker analysis, disease evaluation with the race IB-49 carrying AVR-Pita, and IE-1k not carrying AVR-Pita and sequence analysis. A total of 183 accessions were identified using a Pi-ta indel marker from the intron region. Sequence analysis revealed that resistance functional nucleotide polymorphism (FNP) was present in 163 accessions including reference cultivars. Among them, 89 were resistant to IB-49 and susceptible to IE-1k indicating that these accessions contain the Pi-ta R alleles. Four accessions susceptible to IB-49 suggest that components were not intact in Pi-ta mediated resistance. In contrast, 14 accessions with the susceptible FNP were resistant to IB-49 suggesting these 14 accessions may contain the Pi-ta independent new R gene. Together, 87 accessions were identified that contain the new R gene to IE-1k. These accessions were genetically distinct determined by SSR markers. The results could impact breeding for blast resistance worldwide.