甜瓜黑斑病菌的拮抗细菌筛选、鉴定及发酵条件优化

从健康甜瓜植株的根、茎、叶和果实分离内生细菌,明确优良拮抗菌株的分类地位及其最优发酵条件。利用平板稀释法分离内生细菌,平板对峙法筛选黑斑病菌(Alternaria tenuissima)的优良拮抗细菌,通过形态学和分子生物学鉴定,并使用单因素和正交试验方法优化发酵条件。分离共得到50株内生细菌,21株对细极链格孢具有拮抗作用,11株的抑制率达到70%以上,其中菌株G2的抑菌率最高,达76.41%,室内离体防效达44.90%,经形态特征和基因序列分析鉴定为枯草芽孢杆菌(Bacillus subtilis),其最优发酵培养基为葡萄糖20 g、硝酸钠30 g、酵母膏10 g和水1 000 mL,最优发酵条件为摇床转速150 r/min,温度32℃,150 mL摇瓶装液50 mL,最佳接种量为0.2%,培养基初始pH为7.5,其最佳发酵时间为18 h。该结果为甜瓜黑斑病生物防治提供了菌种资源,也为甜瓜内生细菌G2的产业化开发提供了依据。

Screening,Identification and Fermentation Condition Optimization of an Antagonistic Bacterium for Melon Black Spot

Endophytic bacterial strains were isolated from the roots,stems,leaves and fruits of healthy melon plants,and the taxonomic status and optimal fermentation conditions of the excellent antagonistic strains were clarified.The dilution plate coating was applied to isolate endophytic bacteria,and the plate confrontation was used to screen the excellent antagonistic bacteria for Alternaria tenuissima.Identification was conducted via morphology and molecular biology,and the fermentation conditions were optimized through single-factor and orthogonal experiment.The results showed that total 50 strains of endophytic bacteria were isolated,21 strains of them had antagonistic effects against A.tenuissima,and the inhibition rate by 11 strains reached > 70%.Among them,strain G2 had the highest inhibition rate,reaching 76.41%,indoor in vitro prevention effect reached 44.90%.According to the results of morphological characteristics and gene sequence analysis,strain G2 was identified as Bacillus subtilis.The optimal culture conditions of strain G2 were with a medium included 20 g glucose,30 g sodium nitrate,10 g yeast extract in 1 000 mL water.The optimal fermentation conditions were as followed:shaking 50 mL liquid(the best inoculum size was 0.2%)in an 150 mL flask at 150 r/min at 32℃,with an initial pH value of 7.5,and the optimal fermentation time was 18 h.The results may supply new strain resource for the biological control of melon black spot and also provide a basis for the industrial development of melon endophytic bacterium strain G2.