Interspecific homologous recombination generates genomic and phenotypic diversity in Florida populations of Xanthomonas perforans
E. GOSS (1), J. Jones (2), G. Vallad (2), S. Timilsina (2), N. Potnis (2) (1) University of Florida, U.S.A.; (2) University of Florida, U.S.A.

The long-distance movement of plant material has introduced plant pathogens to new geographic regions and caused the emergence of new diseases. One of the consequences of the global movement of plant pathogens has been hybridization between diverged evolutionary lineages, resulting in recombinant pathogens. Recombinants may exhibit unique phenotypes, including new virulence specificities and expanded host ranges. Over the past 25 years the Xanthomonas population causing bacterial spot of tomato in Florida has undergone two major race shifts even though the corresponding resistance genes were not commercially deployed. We asked what genetic mechanisms and demographic factors could have contributed to these population shifts. Whole genome sequencing of 32 Florida strains of X. perforans revealed that homologous recombination with X. euvesicatoria has generated population genomic variation. All of the strains sequenced from 2006 collections were recombinant and represent multiple independent recombination events. By 2012, two of these recombinant lineages dominated the population causing bacterial spot on tomato, one of which is capable of causing disease on pepper. Variation in bacteriocin production and in multiple effector genes corresponds with strain genetic background. Our identification of independent recombinant genomes suggests that gene flow between these Xanthomonas species is not uncommon and is likely to be generating new bacterial spot pathogens in other tropical and sub-tropical tomato production regions.

Abstract Number: C23-2
Session Type: Concurrent