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ARS Home » Southeast Area » Stuttgart, Arkansas » Dale Bumpers National Rice Research Center » Research » Publications at this Location » Publication #419819
Research Project: Broadening and Strengthening the Genetic Base of Rice for Adaptation to a Changing Climate, Crop Production Systems, and Markets

Location: Dale Bumpers National Rice Research Center

Title: Surveys of Magnaporthe oryzae genotypes in breeding stations and commercial rice fields in Arkansas, Louisiana and Puerto Rico from 2017 to 2019

Author
item HUANG, YIXIAO - Orise Fellow
item Jia, Yulin
item WAMISHE, YESHI - University Of Arkansas
item Jia, Melissa

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2024
Publication Date: 1/12/2025
Citation: Huang, Y., Jia, Y., Wamishe, Y., Jia, M.H. 2025. Surveys of Magnaporthe oryzae genotypes in breeding stations and commercial rice fields in Arkansas, Louisiana and Puerto Rico from 2017 to 2019. Plant Disease. https://doi.org/10.1094/PDIS-03-24-0652-RE.
DOI: https://doi.org/10.1094/PDIS-03-24-0652-RE

Interpretive Summary: Rice blast, caused by fungus Magnaporthe oryzae, is one of the most destructive diseases of rice. Major resistance (R) gene mediated resistance to M. oryzae is often overcome by the fungus due to the occurrences of new races with altered corresponding avirulence (AVR) genes. In this study, we collected regional blast diseased samples from experimental stations and commercial rice fields from Arkansas, Louisiana and Puerto Rico from 2017-2019 to determine the efficacy of major R genes, Pi-ta, Pik, Pizt, Pib, Pi9, and Pi33 in these regions. A total of 185 blast isolates were purified to examine the existence of corresponding AVR genes AVR-Pita1, AVR-Pib, AVR-Pik, AVR-Pizt, AVR-Pi9 and ACE1. AVR-Pizt and AVR-Pita1 were found in all isolates and AVR-Pi9, ACE1 and AVR-Pib were found in most isolates suggesting that major R genes Pizt, Pi-ta, Pizt, Pi33 and Pib are effective to prevent infections by these isolates. Among them, 117 of 185 contain all 6 AVR genes and three other groups contain 3-5 AVR genes suggesting that there exhibit different degrees of race shift in these isolates. To compare the genetic diversity of blast isolates, their genotypes were examined with 10 simple sequence repeat (SSR) markers. SSR data revealed that genetic backgrounds of isolates from Arkansas were endemic but some isolates from Louisiana share the same fingerprints with isolates from Puerto Rico. Genetic structure analysis of SSR data suggests that there are three major clusters with 46 combinations of SSR markers. The isolates in Arkansas showed high genetic diversity dominated by one genotype. The Louisiana isolates were more genetically diversified without any obvious predominant group. The Puerto Rico isolates had the lowest heterozygosity. These data reveal contemporary genetic changes of rice blast fungus and are useful for guiding the deployment of major R genes in these regions.

Technical Abstract: Major resistance (R) gene mediated resistance to rice blast fungus Magnaporthe oryzae is often overcome by the fungus due to the occurrences of new races with altered corresponding avirulence (AVR) genes. In this study, blast diseased rice tissue samples were collected from breeding stations and commercial rice fields in Arkansas, Louisiana, and Puerto Rico during 2017-2019 to determine the efficacy of major R genes, Pi-ta, Pik, Pizt, Pi9, and Pi33. A total of 185 blast isolates were isolated from the diseased tissue samples to examine the existence of AVR genes AVR-Pita1, AVR-Pib, AVR-Pik, AVR-Pizt, AVR-Pi9 and ACE1. Genotyping of the isolates were conducted using 10 simple sequence repeat (SSR) markers. AVR-Pizt and AVR-Pita1 were found in all isolates suggesting that major R genes Pizt and Pi-ta are still effective to prevent infections by these isolates. Among the 185 isolates, 117 contained all the 6 AVR genes and three other groups contained 3-5 AVR genes suggesting various degrees of race shift in these isolates. The SSR data revealed endemicity in genetic backgrounds among isolates from Arkansas, whereas migration in isolates between Louisiana and Puerto Rico. Structure analysis of the SSR data suggested two major clusters with 46 combinations. The Arkansas isolates showed a high genetic diversity but one genotype dominated. The Louisiana isolates were also genetically diversified without any obvious predominant group. The Puerto Rico isolates had the lowest heterozygosity. These data reveal contemporary genetic changes of the rice blast fungus and are useful for guiding the deployment of major R genes in these regions.