马铃薯疮痂病高效生防芽孢杆菌的筛选及发酵条件优化

利用已鉴定的5株拮抗马铃薯黑痣病病原菌的生防芽孢杆菌（Bacillus），筛选其对马铃薯疮痂病病原菌的抑制作用，通过检测生防菌脂肽类抗生素合成相关基因研究其生防机制。对峙试验结果表明，5株生防菌中以QHZ-3对马铃薯疮痂病病原菌的抑制效果最佳，抑菌率为44%；抗生素合成基因检测结果显示，QHZ-1和QHZ-2具有丰原素（Fengycin）和伊枯草菌素（Iturin）合成酶基因；QHZ-4仅具有Fengycin合成酶基因；而QHZ-3与QHZ-5菌株同时具有表面活性素（surfactin）、伊枯草菌素（Iturin）和丰原素（fengycin）3种脂肽类抗生素合成酶基因。选择最具生防潜力的QHZ-3进行进一步试验，发现该菌株发酵滤液对疮痂链霉菌的抑菌圈直径达到30.4 mm，且在高温、紫外照射以及强酸强碱的条件下抑菌圈直径仍然可保持在27 mm以上。单因素试验结果表明，每瓶（250 mL）装液量60 mL，接种量6%，摇床转速180 r·min^-1，发酵时间60 h的条件下，菌株QHZ-3的生长量最高。正交试验结果显示，装液量每瓶40 mL、摇床转速170 r·min^-1、接种量6%、发酵时间48 h的组合下，QHZ-3生长状态最佳，活菌数可达到1.31×10¹⁰ cfu·mL^-1。二次固态发酵条件优化结果显示，以腐熟的牛粪有机肥为载体，在接种量为15%时，活菌数最高，达到1.14×10⁹ cfu·mL^-1。

Screening of highly effective biocontrol Bacillus strains for potato scab and optimization of its fermentation conditions

The incidence of potato scab caused by Streptomyces scabies is increasing in the main potato production regions in Gansu Province. It is urgent to explore safe and effective biological control methods for this disease. This experiment screened the inhibitory effects of the identified 5 strains of Bacillus on potato scab pathogens, which were significantly antagonistic to potato black mole disease pathogens, the biocontrol mechanism was studied by detecting the genes related to the synthesis of biocontrol lipopeptide antibiotics. The results of the confrontation experiment showed that among the five strains of biocontrol bacteria, QHZ-3 had the best inhibitory effect on the pathogen of potato scab, and the inhibition rate was 44%. Antibiotic synthesis gene test results showed that QHZ-1 and QHZ-2 had fengycin and iturin synthase genes. The QHZ-4 had only fengycin synthase genes, and QHZ-3 and QHZ-5 strains had three lipopeptide antibiotic synthetase genes of surfactin gene, iturin gene and fengycin gene. The QHZ-3 with the most biocontrol potential was selected for further study, and it was found that the diameter of the inhibition zone of the fermentation filtrate on Streptomyces scabies reached 30.4 mm, and under the conditions of high temperature, ultraviolet radiation and strong acid and alkali, the diameter of the bacteriostatic circle was still kept above 27 mm. The results of single\|factor experiments showed that the growth rate and antibacterial activity of strain QHZ-3 were the highest under the conditions of 60 mL pre 250 mL triangular flask, 6% inoculation volume, 180 r·min^-1 shaker speed, and 60 h fermentation time. Orthogonal experiment results showed that under the combination condition of 40 mL per triangle flask, shaker speed of 170 r·min^-1, inoculation amount of 6%, and fermentation time of 48 h, QHZ-3 had the best growth state and the number of viable bacteria reached 1.31×10¹⁰ cfu·mL^-1. The results of the optimization of the secondary solid fermentation conditions showed that use the composted cow manure organic fertilizer as the carrier, the number of viable bacteria was the highest when the inoculation amount was 15%, reaching 1.1×10⁹ cfu·mL^-1.