Poster: Biology & Disease Mgmt: Bacteriology
19-P
Comparative genomic analyses of 15 Acidovorax pathogens provide insights into the emergence of a new turfgrass disease and the host specificity
Q. ZENG (1), J. Wang (2), P. Giordano (3), F. Bertels (4), M. Chilvers (5), J. Vargas (5), G. Sundin (5), N. Mitkowski (6) (1) The Connecitcut Agricultural Experiment Station, U.S.A.; (2) Michigan State Univ, U.S.A.; (3) Bayer Corporation, Canada; (4) Uni
Bacterial etiolation and decline (BED), caused by Acidovorax avenae subsp. avenae (Aaa), is an emerging disease of creeping bentgrass on golf course putting greens. The causal agent of BED belongs to the genus Acidovorax, members of which can infect various hosts with strong host specificity. In this research, we aim to understand the emergence of BED, and identify genes in turf Aaa that define its host specificity. Eighteen Acidovorax draft genomes (14 turf, 3 maize, and 1 orchid pathogenic strains) were generated. Using whole genome SNP analysis, the 14 turf-pathogenic Aaa isolates were grouped into three clades. High levels of single nucleotide polymorphisms, gene deletions, insertions, and inversions were detected within the turf-pathogenic Aaa isolates, suggesting that the 2009-2011 BED outbreak was caused by a genetically diverse population. Population genomic analyses identified genes whose sequences are conserved in turfgrass pathogenic Aaa in comparison to the closely related maize pathogenic Aaa isolates. Interestingly, many of these genes identified are located within the type III secretion system pathogenicity island, an important virulence factor of phytopathogenic bacteria. We identified homologous recombination as the potential cause of the gene conservation observed in the T3SS pathogenicity island. Our results suggested a strong host selection during the evolution of the turf-pathogenic Aaa.