Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/25/2016
Publication Date: 7/2/2017
Citation: Jia, Y., Lin, M.J. 2017. Survey of rice blast race identity for blast resistance gene identification in the USA and Puerto Rico. Proc. 36th Rice Technical Working Group Meeting Proceedings, Galveston, TX, p. 89. March 1-4, 2016. CDROM.
Technical Abstract: Rice blast disease is a significant threat to stable rice production in the USA and worldwide. The major resistance gene (Pi-ta) located within a cluster of resistance genes on rice chromosome 12 has been demonstrated to confer resistance to the rice blast disease. Katy, a rice cultivar released in 1989, was the first rice variety incorporating the Pi-ta gene cluster. Since 1989, Katy has been used as the Pi-ta gene cluster donor resulting in the development of more than 10 commercial rice cultivars in the Southern USA. In order to direct breeding for blast resistance, a set of international differential rice cultivars were used to determine the race identity of rice blast field isolates, and the effectiveness of the Katy derived Pi-ta gene cluster in conferring resistance to rice blast disease. The varieties used in our efforts included: Raminad Str. 3, Zenith, NP125, Usen, Dular, Shataotsao, Caloro, Katy, and M202 (the latter, a blast susceptible control). From 2012 until 2014, blast fungal samples were obtained from three primary sources: 1. Diseased rice leaves and/or panicles from commercial rice fields, 2. three rice experiment stations in the Southern USA, and 3. The winter nursery in Puerto Rico (2015). Diseased samples were placed on well-moistened filter-paper under continuous florescent lighting for a period of 12 hours. Subsequently, the conidia were identified with a dissecting microscope, and transferred to water agar plates for purification. Purified spores were grown on filter-paper laid on top of oatmeal media to produce sporulated mycelia. Upon mycelia maturation, the filter papers were desiccated and stored long term at -20°C. Testing rice variety resistance to blast requires inoculating an oatmeal culture with a small section of filter paper containing the mycelia of selected blast fungal isolate. The plate cultures were grown under florescent light for 7 to 10 days in order to produce spores for the inoculation. A total of 74 selected isolates representing 10% of blast collections were evaluated. A total of 9 blast races, IB1, IB17, IB49, IB53, IC1, IC17, IC21, IG1, and IE1 were identified. Among them, IB1, IB49 and IC17 were more commonly found than other races. Katy was resistant and M202 was susceptible to all 74 blast isolates. Katy is known to contain Pi-ta and Pi-ks and M202 contains Pi-ks. These data suggest that the Pi-ta gene cluster in Katy is still effective in preventing blast disease in the USA.