Characterization and identification of bacteria isolated from Lolium perenne and Poa annua / by Yan Liu.

"Bacterial wilt on Lolium perenne and Poa annua caused by Xanthomonas translucens is a major concern on golf courses in the United States. Bacteria were isolated from both L. perenne and P. annua suffering bacterial wilt and were confirmed as the causal agents via Koch's postulates. Generation time of each bacterial isolate was measured at 250 C, 300 C and 350 C, respectively. Temperature influence on disease severity on both L. perenne and P. annua were evaluated at 25/180 C, 30/230 C and 35/280 C, respectively. Results revealed that the shortest generation time of each bacterial isolate was measured at 350 C, bacterial isolates were more pathogenic to the host from which they were isolated and varieties in virulence did exist in both L. perenne bacterial isolates and P. annua bacterial isolates. A positive correlation between temperature and disease severity was discovered on both L. perenne and P. annua. Results also revealed that L. perenne bacterial isolate, r3, is different from other bacterial isolates at many aspects. The 16S rDNA identification using a 1276-bp 16S rDNA sequence and the multilocus sequence analysis (MLSA) using a 1803-bp concatenated sequence of four housekeeping genes (gyrB, fusA, gapA and lepA) demonstrated that the L. perenne bacterial isolates, r0 and r5, were X. translucens pv. graminis and the P. annua bacterial isolates, p0, p6 and p8, were X. translucens pv. poae and suggested that the L. perenne bacterial isolate, r3, may be a new Xanthomonas species."--Page ii.

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