农用植物酵素液中梨树腐烂病菌拮抗细菌的筛选和防病效果

从农用植物酵素液中筛选对梨黑腐皮壳菌（Valsa pyri）具有抑菌活性的细菌菌株，明确其对梨树腐烂病的防治潜力，以梨黑腐皮壳菌为靶标菌，通过平板对峙培养和牛津杯法从分离自农用植物酵素液的细菌中筛选拮抗菌株，并分析拮抗菌株对病原菌孢子萌发和菌丝生长的影响及防病效果。结果表明，从农用植物酵素液中分离的68株细菌中初筛出15株对梨黑腐皮壳菌具有抑菌作用的细菌，占分离菌株数的22.1%，抑菌率为41.25%～74.14%。经过复筛，4个菌株（gjfn2、gjfn4、PFN41、PGY-FX67）的发酵液和除菌发酵滤液抑菌率分别大于70%和60%，显著高于其他菌株。采用形态特征、生理生化特性及16S rRNA和gyrA基因序列分析，将gjfn2、gjfn4和PGY-FX67鉴定为贝莱斯芽孢杆菌（Bacillus velezensis），PFN41鉴定为解淀粉芽孢杆菌（Bacillus amyloliquefaciens）。4个拮抗菌株发酵液和除菌发酵滤液对梨黑腐皮壳菌分生孢子的萌发有明显的抑制作用，gjfn4、PFN41菌株发酵液及除菌发酵滤液对梨黑腐皮壳菌分生孢子的抑制率36 h均可达到100%，并使梨黑腐皮壳菌菌丝形态畸形、弯曲、末端膨大。离体枝条法防效测定结果表明，4个菌株的发酵液防效均达到79%以上，除菌发酵滤液防效均达到73%以上，其中gjfn4菌株的防效最佳，其发酵液、除菌发酵滤液及除菌发酵滤液50倍稀释液对梨树腐烂病防效分别均达到84.79%、81.57%和67.27%。由此表明，从农用植物酵素液中筛选获得的拮抗细菌菌株具有防治梨树腐烂病的良好潜力。

Screening of Antagonistic Bacteria Against Valsa pyri from Agricultural Plant Jiaosu and Their Control Effects on Pear Canker

To screen antagonistic bacteria strains against Valsa pyri from agricultural plant Jiaosu and evaluate their biocontrol potential on pear canker, bacteria strains isolated from agricultural plant Jiaosu were screened by confrontation culture and oxford cup method. The inhibitory activities of bacteria strains against the conidia germination and mycelia growth of V. pyri and their biocontrol effects on pear canker were evaluated. The results showed that 15 strains of 68 bacterial strains isolated from agricultural plant Jiaosu had antagonistic effects on V. pyri growth with the inhibitive rate from 41.25% to 74.14%, which accounted for 22.1% of isolated strains. Four strains (gjfn2, gjfn4, PFN41 and PGY-FX67) were obtained after the second run screening, and the inhibition rates of their fermentation and filtered fermentation both were over 70% and 60%, respectively, which were significantly higher than those of the other strains. Based on morphological, physiological and biochemical characteristics, 16S rRNA and gyrA gene sequence analysis, gjfn2, gjfn4 and PGY-FX67 were identified as Bacillus velezensis and PFN41 was as Bacillus amyloliquefaciens. The fermentation and filtered fermentation broth of the four antagonistic bacteria strains had obviously inhibitive effects on V. pyri conidia germination. And the inhibitive rate of the fermentation and filtered fermentation broth of gjfn4 and PFN41 strains reached 100% after 36 h incubation, and it also could cause the morphological abnormality, bent and terminal enlargement of the V. pyri mycelia. In detached twigs assay, the control effects of fermentation broths of the four strains were over 79% and filtered fermentation broths were over 73%. Among them, gjfn4 had the best control effect on pear canker, which the control effects of fermentation broth, filtered fermentation broth and 50 dilution of filtered fermentation broth were 84.79%, 81.57% and 67.27% respectively. The results indicated that the antagonistic bacteria strains screened from agricultural plant Jiaosu exhibited significant biocontrol potential to control pear canker, which provided a novel biological agent for control the disease.