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ARS Home » Southeast Area » Stuttgart, Arkansas » Dale Bumpers National Rice Research Center » Research » Publications at this Location » Publication #324110
Title: First report of multiple races of the rice blast fungus Magnaporthe oryzae in Puerto Rico

Author
item Jia, Yulin
item McClung, Anna

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2016
Publication Date: 3/21/2016
Citation: Jia, Y., McClung, A.M. 2016. First report of multiple races of the rice blast fungus Magnaporthe oryzae in Puerto Rico. Plant Disease. doi: 10.1094/PDIS-12-15-1391-PDN.

Interpretive Summary: The rice nursery located in the Lajas Valley, in the southwestern corner of Puerto Rico has been used by US rice breeders for the past 43 years to produce one to two extra generations per year. In the present study, rice blast disease was positively identified from rice panicles harvested in Puerto Rico in April 2015. A total of 28 isolates were purified from disease like lesions on the panicles, and 20 of which were determined to belong to 4 races of rice blast, IB1, IB17, IB49 and IB53. Further pathogenicity and molecular analysis revealed that these isolates were highly similar to isolates commonly found in the US. Rice varieties which possess the major Pi-ta blast resistance gene cluster will be useful for preventing infections from these isolates. Thus, we show that the Puerto Rico winter nursery serves rice breeders by offering an opportunity to select for blast disease resistance as well as other agronomic traits. In addition, as some commercial production of rice is being re-established on the island, our study suggests that the Pi-ta gene cluster found in several southern US rice cultivars, like Katy, will be effective for blast control in Puerto Rico.

Technical Abstract: The rice nursery located in the Lajas Valley, in the southwestern corner of Puerto Rico has been used by US rice breeders for the past 43 years to produce one to two extra generations per year. In April, 2015, blast disease lesions were observed on rice breeding lines belonging to the USDA ARS DB NRRC and to the University of Arkansas Rice Research and Extension Center. The fungal mycelia with three celled asexual spores typical of the rice blast fungus Magnaporthe oryzae were positively identified from diseased panicles. A total of 28 isolates were purified from these lesions, and 20 of which were determined to belong to 4 races, IB1, IB17, IB49, and IB53. Further pathogenicity tests with a set of international differential cultivars and molecular analysis with avirulence gene-specific PCR primers revealed that these isolates were highly similar to isolates commonly found in the US and the deployed major Pi-ta gene cluster is useful for preventing infections of these isolates. Thus, we show that the Puerto Rico winter nursery serves rice breeders by offering an opportunity to select for blast disease resistance as well as other traits. Although one isolate from Puerto Rico, belonging to IB49, was mentioned in previous literature, the location and time of the occurrence of rice blast has not been reported. To our knowledge this is the first report of multiple races of the rice blast pathogen in Puerto Rico. In addition, as some commercial production of rice is being re-established on the island, our study suggests that the Pi-ta gene cluster found in a US adapted tropical japonica cultivar Katy will be effective for blast control in Puerto Rico.