核盘菌菌核围微生物群落分析及其对盾壳霉重寄生的影响

Microbial community analysis of Sclerotinia sclerotiorum and its effect on the mycoparasitism of Coniothyrium minitans

重寄生真菌盾壳霉(Coniothyrium minitans)是核盘菌的一种生防菌,它通过寄生核盘菌菌核,减少初侵染来源,从而达到防病效果。但在田间自然土壤中,核盘菌菌核围微生物对盾壳霉寄生菌核的影响还不清楚。本研究对核盘菌菌核围微生物进行了分离鉴定,并评估了菌核围细菌对盾壳霉重寄生的影响。结果表明,不同取样时间和不同深度的核盘菌菌核围土壤中,均存在可培养微生物富集的"菌核围效应",即菌核围土壤中可培养细菌数量和真菌数量均高于非菌核围土壤。从菌核围土壤中共分离获得了253株细菌和180株真菌,并对其中的代表菌株进行了分子鉴定,发现假单胞菌属(Pseudomonas)和芽胞杆菌属(Bacillus)是菌核围细菌的优势种群,青霉属(Penicillium)是菌核围真菌的优势种群。通过平板对峙,从菌核围细菌中筛选到25个菌株对核盘菌有拮抗活性,22个菌株对盾壳霉具有拮抗活性。砂皿寄生菌核试验证实,7株菌核围细菌对盾壳霉寄生菌核有显著的抑制作用。核盘菌菌核围细菌对盾壳霉重寄生的抑制作用,可能是导致盾壳霉田间生防效果不稳定的原因之一。

Coniothyrium minitans is a mycoparasite of the plant pathogenic fungus Sclerotinia sclerotiorum. It can parasitize sclerotia of S. sclerotiorum, reducing apothecial production and disease incidence. However, in the natural soils, the effect of sclerosphere microbes on infection of S. sclerotiorum sclerotia by C. minitans is poorly understood. This study was focused on the ecology of the sclerosphere microorganism community of S. sclerotiorum sclerotia, using isolation and molecular techniques. We analyzed the sclerosphere microorganism community of S. sclerotiorum in different treatments, including sampling time and burial depth of sclerotia. Results showed that the populations of bacteria and fungi in sclerosphere soil were significantly higher than those in sclerotia-free soils. Two hundred and fifty-three bacteria and one hundred and eighty fungi were isolated from sclerosphere soil. Base on bacterial 16 S rDNA and fungal internal transcribed spacer of ribosomal DNA sequences, we identified Pseudomonas and Bacillus as the dominant bacterial populations in the sclerosphere. Whereas, Penicillium was the dominant fungus population in the sclerosphere. In the dual culture in vitro assays, there were 25 and 22 sclerosphere bacterial strains with antagonistic activity against S. sclerotiorum and C. minitans, respectively. Furthermore, sclerotial infection assay showed that seven bacterial strains significantly suppressed infection of sclerotia by C. minitans in vitro. These results suggest that in the field, sclerosphere bacteria might play an important role in suppression of the infection of sclerotia by C. minitans.