Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/29/2004
Publication Date: 2/1/2005
Citation: Jia, Y., Wang, Z., Fjellstrom, R.G., Moldenhauer, K., Flowers, C.B., Rutger, J.N. 2005. Rice pi-ta gene confers resistance to two major pathotypes of the rice blast fungus in the U.S. [abstract]. Rice Technical Working Group Meeting Proceedings. Abstract p. 84. Interpretive Summary:
Technical Abstract: Blast is a serious rice disease in the Southern US. The Pi-ta gene in rice prevents the infections of Magnaporthe grisea isolates containing the avirulence AVR-Pita gene. Pi-ta encodes a putative cytoplasmic receptor that appears to bind to a predicted processed AVR-Pita to elicit a defense response. The landrace cultivar Tetep was the donor for the Pi-ta gene for the US cultivar, Katy. Subsequently, Katy was the Pi-ta donor for additional US cultivars, Drew and Kaybonnet. The objective of this study is to determine the role of Pi-ta in resistance to contemporary blast pathogen races in the Southern US. Field surveys have indicated that the races IB-49 and IC-17 are the most common in the Southern US. We observed that all of the Pi-ta containing cultivars were resistant to both major pathotypes IB-49 and IC-17 of M. grisea. The presence of Pi-ta as determined by DNA markers for the Pi-ta gene completely correlated with resistance to both IB-49 and IC-17. The resistance was further investigated using a marker for the resistant Pi-ta allele in a F2 population of 1345 progeny of a cross with Katy. Resistance to IC-17 was conferred by a single dominant gene, and Pi-ta was not detected in susceptible individuals. Another F2 population of 377 individuals of a reciprocal cross was used to verify the conclusion that resistance to IC-17 was conferred by a single dominant gene. In this cross, individuals resistant to IC-17 were also resistant to IB-49. The presence of Pi-ta and resistance to IB-49 was also correlated with additional crosses involving another Pi-ta containing rice culitvar. A pair of primers that specifically amplifies a susceptible pi-ta allele was developed to verify the absence of the dominant Pi-ta gene. These data suggest that Pi-ta is responsible for resistance to IB-49 and IC-17. The correlation of Pi-ta with resistance to both M. grisea pathotypes suggests they contain functional AVR-Pita genes. Currently, structural and functional analysis of AVR-Pita alleles from IB-49 and IC-17 are in progress. Completion of this task will enhance the understanding of molecular evolution of the AVR-Pita gene. In the future, DNA markers for Pi-ta can be used to follow the incorporation of Pi-ta into advanced breeding lines containing additional blast resistance genes to reach a broad spectrum of resistance to different fungal isolates.