P-553 - The AVR gene profiles of Magnaporthe oryzae in Arkansas: Insights from the 2024 crop season

Monday, August 4, 2025

4:30 PM - 5:15 PM HST

Location: Exhibit Hall 3

Presenting Author(s)

SD

Samuel De Paula

Postdoctoral Fellow
University of Arkansas
Stuttgart, AR, USA

Author(s)

SB

Scott Belmar

Program Technician
University of Arkansas
Stuttgart, Arkansas, United States
AF

Ana C.B. Ferreira

Visiting Scholar
University of Arkansas System Division of Agriculture
Stuttgart, Arkansas, United States
JP

Jocilene S. Pereira

Visiting Scholar
University of Arkansas System Division of Agriculture
Stuttgart, Arkansas, United States
YH

Yixiao Huang

Postdoctoral Research Associate
USDA ARS Dale Bumpers National Rice Research Center (DB NRRC)
Stuttgart, Arkansas, United States
RP

Rodrigo Pedrozo

Postdoctoral Research Associate
USDA ARS Dale Bumpers National Rice Research Center (DB NRRC)
Stuttgart, Arkansas, United States
YJ

Yulin Jia

Research Leader/Center Director/Location Coordinator
USDA ARS Dale Bumpers National Rice Research Center (DB NRRC)
Stuttgart, Arkansas, United States
XS

Xueyan Sha

Professor of Plant Rice and Genetics
University of Arkansas
Stuttgart, Arkansas, United States
CN

Camila Nicolli, PhD

Assistant Professor - Extension Plant Pathologist
University of Arkansas
Stuttgart, Arkansas, United States

Abstract Text: Rice blast disease, caused by the fungus Magnaporthe oryzae, represents a major threat to rice production, leading to noticeable yield losses. Genetic resistance remains the most effective management strategy. Major rice resistance (R) genes recognize the corresponding M. oryzae avirulence (AVR) genes, triggering a robust host-resistant response. However, shifts in AVR gene profiles can compromise the efficacy of deployed R genes, undermining resistant varieties. Therefore, this study aimed to conduct a survey of rice blast fungus in Arkansas, USA, during the 2024 crop season to assess potential changes in pathogen dynamics. Blast samples were collected from 5 varieties distributed in 22 fields across 12 counties and processed using standard isolation techniques. Single spore isolates were stored on desiccated filter papers at -20ºC. Isolates were grown on rice bran agar medium for 10 days and DNA was extracted from mycelia. AVR-Pita1, AVR-Pib, AVR-Pi9, AVR-Pizt, AVR-Pii, and ACE1 were detected through gene-specific primers. All PCR reactions were executed with Taq 2x Master Mix, followed by 2.0% agarose gel electrophoresis. A total of 132 isolates were analyzed, and all six tested AVR genes were detected in 121 isolates, which represents 92% of the population analyzed. AVR-Pi9, AVR-Pii, and AVR-Pizt were not detected in 1, 3, and 7 isolates, respectively. In summary, a high frequency of all tested AVR genes was observed for M. oryzae isolates. The continuous monitoring of AVR gene shifts is crucial for predicting potential impacts on the effectiveness of deployed R genes.