Studies On Diversity Of Botrytis Cinerea Isolated From Tomato And Strawberry

Gray mold caused by Botrytis spp. is an important disease on various crops, including tomato and strawberry. The disease usually causes serious economic losses once it happens. In this thesis, gray mold from tomato and strawberry in greenhouse in Hubei Province was collected and isolated for evaluation of the diversity using various methods such as fenhexamid-sensitivity grouping, detection of transposons and Bc-hch-typing. Following results have been achieved:(1) A total of 759 Botrytis isolates were obtained from tomato and strawberry(393 isolates from tomato and 366 isolates from strawberry). Among them, 753 Botrytis isolates produced black sclerotia, five Botrytis isolates produced yellow sclerotia, one Botrytis isolate produced yellow-black sclerotia(delayed melanization).(2) The 753 black-sclerotial isolates of Botrytis were identified using the B. cinereaspecific primers Bc-f/Bc-r and other molecular methods. The results showed that 751 isolates belonged to B. cinerea, suggesting that the B. cinerea is the dominant species on the two crops in Hubei Province.(3) The 753 Botrytis isolates were determined for the presence of transposons(Boty, Flipper or Boty + Flipper) by PCR. The results showed that B. cinerea population consists of four types: Type I with Boty, type II with Flipper, type III without Boty and Flipper, and type IV with both Boty and Flipper. Among the 390 Botrytis isolates from tomato, 33, 59, 17 and 281 isolates belonged to type I, type II, type III and type IV, respectively. Among the 363 Botrytis isolates from strawberry, 40, 82, 6 and 235 isolates belonged to type I, type II, type III and type IV, respectively. The presence of the transposons has not correlations with the host plants and the geographic locations.(4) The 753 Botrytis isolates were tested for sensitivity to the fungicide fenhexamid(2 μg a.i./m L). The results showed that 504 isolates(256 from tomato, 248 from strawberry) were highly sensitive, 138 isolates(87 from tomato, 51 from strawberry) were moderately sensitive, 110 isolates(46 from tomato, 64 from strawberry) were weakly sensitive and only one isolate from tomato was resistant. The 753 Botrytis isolates were also determined for the Bc-hch-RFLP-typing, which has been found to be correlated with fenheximid-sensitivity in B. cinerea. The groups were identified, 752 isolates showed six DNA bands(517, 287, 155, 119, 84 and 9 bp), whereas HBtom-116 had five DNA bands(601, 287, 155, 119 and 9 bp).(5) Two Botrytis isolates HBtom-116 and HBstr-336 were further identified based on morphological characteristics, sensitivity to fenhexamid, Bc-hch-RLFP typing and molecular features. The results showed that, isolate HBtom-116 was identified as B. pseudocinerea, and isolate HBstr-336 was identified as B. caroliniana.Theses results provided useful information for understanding of the population characteristics of Botrytis on tomato and strawberry in China.