| Gray mold caused by Botrytis cinerea Pers.is a severe and constant disease on tomato plants,the disease results in heavy losses of yield in most tomato producing area of China. 819 bacterial strains were isolated from tomato plants infected and uninfected by Botrytis cinerea Pers.in fields infected by B.cinerea.In all,116 stains of all isolates were found to be antagonistic to Botrytis cinerea Through In vitro antibiosis experiments,which accounted for 14.16%of the total isolates.The activities of protease,cellulase,chitinase and production of siderophores and plant growth hormone indole acetic acid(IAA) for the selected 116 antagonistic isolates were carried out.The diversity of the 116 antagonistic bacteria was characterized with molecular fingerprints by employing amplified ribosomal DNA restriction analysis(ARDRA) and the more discriminating BOX-PCR fingerprint method.On the basis of these works,31 antagonistic isolates were selected for the greenhouse experiment in order to study their biocontrol efficacy.Results showed that all the 31 selected antagonistic isolates showed biocontrol efficiencies of 8.06-67.80%.Then 13 strains with over 50%biocontrol efficiencies were picked for further two times greenhouse biocontrol and growth promoting experiments.The results showed that,except for strain AB 16,other 12 strains' biocontrol efficiencies had obviously coherence with the results of the first greenhouse experiment and revealed the significance compared with control 1(infected with pathogen only) at P＜0.05.Among them,the biocontrol efficieneies of strains ABc28 and ABe22 reached 66.71%and 64.90%respectively.The growth promoting experiment showed that,except for strains ABc1,ABc0,AB16 and AB31,other strains exhibited capacity of promotion for plants growth more or less.Among them,the biomass increase of ABc22 treated tomatoes reached 66.34%.It is worthwhile to mention that not only the biocontrol efficiencies of strains ABe28,ABe22,ABc11 and ABc17 were all above 50%,and their growth promoting effects were also over 20%.They really have good commercial potential.To our knowledge,this study is the first time to report Pseudomonas putida(AB35) and Chryseobacterium sp.(ABc1) can be used as biocontrol agents against B.cinerea on tomato plants.We also studied that three Bacillus spp.(Wenshan 1-18,12LR54 and 2FG34) strains' ability to control bacterial wilt of tomato plants were attributed to induced systemic resistance.When treated on tomato plants,they reduced bacterial wilt of tomato plants by 41.3-44.1%,42.3-43.0%and 41.8-46.7%respectively,the fresh weight of tomato plants increased by 19.60%,22.19%and 26.85%respectively.In vitro antibiosis experiments indicated that there was no inhibition zone between each strain and pathogen HB10,and this indicated each strain's biocontrol efficiency was not due to the antibiosis with pathogen. Bacterial colonization experiments indicated they were remained spatially separated between each strain and R.solanacearum HB10,so we concluded that the disease control was attributed to strain's ability to induce systemic resistance against R.solanacearum. Enzyme activity assays further indicated that after applying with each strain and inoculating with R.solanacearum HB 10,they could increase the activities of PAL,SOD,PPO,PAL and PPO respectively,the overall effect was that it increased the activities of related enzymes. Especially,we further analyzed strain Wenshan 1-18's mechanisms of both protection against pathogens and plant growth promotion.RT-PCR monitored the defensive related gene PR1α(related to defense) and growth-related gene Exp2(related to growth promoting) expressed rapidly when treated with Wenshan 1-18.Wenshan 1-18 could also produce IAA and utilize phosphorus(promoting plant growth ) In vitro. |
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