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Oral: Bacterial Disease Management


Whole genome sequencing of Xanthomonas perforans identifies effectors that influence breeding strategies
S. TIMILSINA (1), P. Abrahamian (2), N. Potnis (3), G. Minsavage (4), F. White (4), B. Staskawicz (5), J. Jones (4), G. Vallad (4), E. Goss (4) (1) University of Florida, U.S.A.; (2) Gulf Coast Research and Education Center, University of Florida, U.S.A.;

The management of bacterial spot caused by X. perforans on tomato is a challenge due to historical changes in the pathogen populations. The availability of genomic sequence for hosts and pathogens provides new data for effector-based breeding strategies. We examined the stability and evolution of several effectors in X. perforans, based on genome sequence from representative strains collected in Florida since 1990. Effectors AvrXv3 and XopJ4 trigger resistance in tomato cultivars carrying the corresponding R genes. However, the Florida X. perforans population has shifted from tomato race 3 to tomato race 4, such that avrXv3 is non-functional in all tomato race 4 strains with mutations specific to different phylogenetic groups. The X. perforans effector genes xopJ4 and avrBs2 remain intact in all strains. The avrBsT gene is absent in race 3 strains collected in the 1990s, but present in race 3 strains collected in 2006 and the majority of race 4 strains. The conserved presence of XopJ4 and increased presence of AvrBsT among race 4 strains of X. perforans make them ideal targets for resistance breeding. Specific R-genes against these two effectors could be pyramided with Bs2 resistance to develop tomato cultivars with enhanced resistance against X. perforans for commercial production in Florida.