Study On Phyllosphere Bacteria Of Xa21 Transgenic Rice

The molecular method to identify Xanthomonas oryzae pv.oryzae (Xoo) was built in this study. The dynamic changes of three Xoo strains in greenhouse and the phyllosphere bacterial communities in field trial of three rice varieties {Xa21 transgenic rice, unmodified control rice Wan A and conventional rice variety Shanyou 63) were studied.Seven Xoo strains were compared by their ITS (Intergenic spacer region) sequences, IS-PCR fingerprint and SDS-PAGE of total strains' proteins. The Length of all the seven strains' ITS sequences was 492 bp (Accession number AY250998-AY251004), only with four sites difference.The SDS-PAGE fingerprints of seven strains' total bacterial proteins were very similar except strain C5. Seven strains were divided into three groups by their IS-PCR fingerprints. The two bands appeared in all the strains were sequenced to 244bp and 489bp, respectively. Depended on the sequence of the band of 489bp, a pair of prime was designed to amplify the specific band of 355bp for all the seven strains. Based on the primes and IS-PCR fingerprints, the community of Xoo in the Xa21 transgenic rice cultivated with a long time could be analyzed rapidly.The differences of Xoo strains' abilities to infect and colonize in phyllosphere of three rice varieties were studied. After inoculation by clipping method, the numbers of Xoo increased rapidly in three rice varieties in the early time until it reached about 106CFU/leaf. The number of Xoo decreased in the Xa21 transgenic rice but increased 100-1000 fold in the other two rice varieties after that. When spraied in rice leaves, all the three Xoo strains could survive for a long time, but no significant differences among those three rice varieties were found.The phyllosphere bacterial communities of the rice varieties were studied in field trial. Significant differences were found among the total number of bacterial communities in different blocks at the same time, but no differences among three rice varieties were found. Significant differences were also found among the total number of phyllosphere bacterial communities of each rice variety in different time, but not among rice varieties at the each time. Twelve bacterial strains isolated from the rice phyllosphere were divided into eight genus by their ITS sequence (Accession number AY485405-AY485416).The predominance genus in phyllosphere of all three rice varieties were Clavibacter, Bacillus and Xanthomonas. Significant differences were found among the diversity indexes of bacterial communities of different time calculated based on genus, but no difference among the varieties at the each time were found.