| Cruciferous clubroot is seriously widespread in Shanghai. The farmers lack awareness of prevention and without effective ways for controlling clubroot, which resulted in great loss to production of cruciferous crops.Through the investigation in the main growing areas of cruciferous in Shanghai, Minhang and Pudong district were the most severe regions that clubroot occurred in Shanghai, with incidence rate 62% and 42%, respectively. And clubroot incidence at the junction of district was obviously higher than that in internal area in Shanghai.Results of pot experiment showed that clubroot control effeciciency of treatment group "QX", "QT", "Q", "XF1", "T4" and"XT" were 100%,100%,93.2%,63.1%, 79.3%and 44.9%, respectively. However, in field trial, control efficiency of each treatment group to clubroot were 70.1%,65.3%,57.8%,51.1%,43.3% and 56.1%, respectively. As the results showed, the combination of bio-pesticides and chemical pesticides applied to clubroot management had a better control effect than various agents administered alone. There was a big difference of control efficiency of Trichoderma harzianum T4 to clubroot both in pot experiement and trial experiment. However, control efficiency of Bacillus subtilis XF-1 and cyazofamid to clubroot were the same in the pot experiment and trial experiment. Therefore, cyazofamid combination with Bacillus subtilis XF-1 and Trichoderma harzianum T4 respectively could control the clubroot more effectively than other treatment groups.The results of biomass detecting suggested that Trichoderma harzianum T4 could promote the fresh weight of Brassica Chinensis more obviously than Bacillus subtilis XF-l(p<0.05), which was just the opposite to the result of plant height. And cyazofamid could promote both of fresh weight and plant height efficiently. However, the control efficiency would be better than other treatment groups when cyazofamid used combination with Trichoderma harzianum T4 or Bacillus subtilis XF-1 respectively.Research of regularty of clubroot epidemic suggested that pH6.5-7.5, soil moisture 20%-30%, and the temperature 23-28℃ were frequently occurrence envoriment for clubroot.DNA was extracted from rhizosphere soil of Brassica Chinensis in pot experiment and fingerprinted by terminal restriction fragment length polymorphism (T-RFLP). Great changes have happened to the structure of microbial communities when the pesticides were poured into the soil. Differences of changes of microbial communities between treatment group with no spores of P. brassicae ("ZC") and control treatment group "SW" were significiant, which suggested that growth of P.brassicae was closely related to microbial communities in rhizosphere soil of Brassica Chinensis. Aanlysis of nMDS (non-metric multidimensional scaling)test, CLUSTER test and SIMPER (Similarity Percentages) test based on Primer 5.0 suggested Bacillus subtilis XF-1 could not only inhibit the Av.Abund of TRF62 and TRF291 but also promote the Av.Abund of TRF307 obviously. Trichoderma harzianum T4 could inhibit the Av.Abund of TRF62, TRF291 and TRF231. However, cyazofamid could only inhibit the Av.Abund of TRF231. The results showed that cyazofamid could affect the growth of p.brassicae mostly by inhibiting the germination of spores of p. brassicae. Bacillus subtilis XF-1 had the same effect as Trichoderma harzianum T4 at the respect of inhibiting the germination of p. brassicae. And effect of Trichoderma harzianum T4 to dominate microbial communities was more significant than Bacillus subtilis XF-1, which may be responsible for the difference in their control efficiency to clubroot.Dominate communities as Bacillus sp. and Streptococcus sp. that TRF307 represented showed greater effect of inhibitation to the growth of P. brassicae than TRF196 and TRF234 represented. On the other hand, microbial communities such as Deinococcus sp., Bacillus sp., and Acidiphilium sp. that TRF62, TRF206 and TRF 231 represented respectively showed the effect of promotion to the growth of P. brassicae more obviously than others. Biofungicide XF-1 and T4 could inhibit the growth of some microbial communities which promoted the growth of P. brassicae. Furthermore, XF-1 could also promote the growth of Bacillus sp. and Streptococcus sp. that TRF307 represents. From the promoting effect or inhibiting effect of pesticides to the growth of p.brassicae, conclusion could be obtained that changes of those microbial communities would affect the control efficiency of biofungicide XF-1 and T4 to clubroot indirectly.Study first obtained the disease incidence and distribution of cruciferous clubroot in Shanghai. And the integrated management techniques that suitbale for clubroot in Shanghai was also estabilished. Reseach described the influence effect of each pesticide to changes of different microbial communities in rhizosphere soil. Reseach also discussed of the relationship between changes of microbial communities and clubroot occurrence, which provided important theoretical explanations and technical support for controlling clubroot of each pesticide. |
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