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Characterization of host resistance and Asian soybean rust (ASR) pathogen variability for durable resistance
P. TIAN (1), S. Smith (1). (1) Univ of Georgia, Athens, GA, U.S.A.

<i>Phakopsora pachyrhizi</i> is the causal agent of Asian soybean rust (ASR) and one of the most aggressive soybean diseases. Resistance to ASR is controlled by five resistance genes (<i>Rpp1-5</i>) shown to be ineffective when challenged with different isolates of <i>P. pachyrhizi</i>. Knowledge of the genetics of resistance to ASR and the variability of ASR populations are essential in dissecting the relationship between the host and pathogen, and developing effective breeding strategies for resistance. This project has three major research components: 1) characterization of soybean and its wild progenitors host resistance, 2) analysis of Asian soybean rust pathogen variability, and 3) integration of host and pathogen datasets to establish pipelines for the release of resistant cultivars. We collected 8 ASR field isolates from 5 different locations in Georgia from 2011-2013. 20 ASR genotypes were identified at the 5 locations. Additionally, the resistance of 16 released Georgia cultivars and 8 soybean progenitors were tested in response to inoculation with the ASR Georgia field isolates. The soybean progenitors demonstrated different levels of resistance. Conversely, all of the released soybean cultivars were susceptible. By using RNA sequencing techniques, we will identify candidate pathogenicity genes in the ASR isolates and specific resistance genes that can potentially be used to develop durable broad-spectrum disease resistance strategies for soybean cultivars grown in Georgia.

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