Evaluation Of Diversity And Biocontrol Potential Of The Endophytic Bacteria In Brassica Napus

Endophytes are the organisms living for all or part of their life cycle within plant tissues but causing no obvious disease to the plants. Endophytic bacteria are ubiquitous with many biological effects reported. This research aimed at analyzing the diversity of the endophytic bacteria in the oilseed rapes(Brassica napus) in Wuhan, to get the isolates which could promote growth of oilseed rape or to inhibit Sclerotinia sclerotiorum, and to evaluate their biocontrol potential. The main results are shown below:1. A total of 134 endophytic bacteria were isolated from different tissues of oilseed rapes in Wuhan. Based on 16 S rDNA sequences, the isolates were identified as 33 species in 18 genera. Among them, isolates in Bacillus(46.27%), Pseudomonas(15.67%) and Stenotrophomonas(11.94%) are the dominants. Diversity analysis showed that Shannon Indices of the endophytic bacteria in roots, stems and leaves were 2.847, 2.808 and 2.356, respectively. The Simpson Indices of the endophytic bacteria in roots, stems and leaves were 0.956, 0.939 and 0.907, respectively. These results suggest that the diversity level of the endophytic bacteria in roots is higher than that in other two tissues. Simpson Index of the whole endophytic bacteriawas 0.936, suggesting that oilseed rape has highly diversified endophytic bacteria.2. In the pot experiment, we found 4 isolates could increase the dry weight of oilseed seedlings. They are CanR-81, CanR-74, CanS-3 and CanL-233. By the dual culture test and the trials on oilseed leaves in vitro, we got 3 antagonistic endophytic bacteria which exhibited antifungal activity against S. sclerotiorum. They are Can L-30, CanR-75 and CanR-76.4. The biocontrol potential of the three antagonistic endophytic bacteria were evaluated on the culture media, oilseed rape leaves in vitro and leaves on oilseed rape seedlings. Isolate CanL-30 showed high efficacy in inhibition of infection of leaves of oilseed rape by S. sclerotiorum. Production of antifungal substances by isolate Can L-30 was found to be responsible for the effective biological control of S. sclerotiorum.These results suggest that selected endophytic bacteria have poteitial to used as biocontrol agents to control sclerotinia stem rot of oilseed rape.