撑绿杂交竹基腐病生防菌的促生机制

Growth-Promoting Mechanism of Biocontrol Bacteria against Bambusa pervariabilis×Dendrocalamopsis grandis Basal Rot

【目的】探究已筛选出的贝莱斯芽孢杆菌(Bacillus velezensis BD2231)和奇异链霉菌(Streptomyces mirabilis BD2233)2株拮抗菌的促生特性及其机制,为杂交竹基腐病防治和植物生长提供有效的微生物菌剂。【方法】采用定性和定量方法,测定BD2231和BD2233在分泌吲哚乙酸(IAA)、溶磷、产铁载体、生物固氮、产ACC脱氨酶和纤维素酶等方面的能力;分析2株菌株对番茄和烟草种子萌发以及对番茄、烟草和杂交竹幼苗生长的影响;利用ELISA试剂盒和实时荧光定量PCR方法,探究菌株对番茄、烟草和杂交竹叶片生长素、赤霉素、水杨酸和茉莉酸的质量浓度及其相关基因表达的影响。【结果】BD2231和BD2233均能产生生长素(IAA)、铁载体和纤维素酶,但不具有溶磷、生物固氮和产ACC脱氨酶的能力,其中,BD2233分泌IAA的质量浓度达12.44 mg·L^(-1),BD2231的载体活性单位(SU)和纤维素酶活性(CMC酶活)分别达26.75%和0.43 U·mL^(-1)。2株菌株可显著促进番茄和烟草种子萌发,经BD2231发酵液处理的番茄和烟草种子发芽率更高,分别为61%和87%。2株菌株可显著促进杂交竹幼苗生长,提高植物的株高、茎粗、鲜质量和干质量。BD2231和BD2233能够显著促进植物叶片内源激素生长素、赤霉素、水杨酸和茉莉酸途径相关基因IAA9、GA20ox、PR-1和MYC2的表达,提高内源激素的质量浓度,BD2233对植物的生长素质量浓度提高效果较好,BD2231对植物的赤霉素、水杨酸和茉莉酸质量浓度提高效果较好。【结论】贝莱斯芽孢杆菌BD2231和奇异链霉菌BD2233通过产生IAA、铁载体和纤维素酶促进植物种子萌发和幼苗生长,且可提高植物生长素、赤霉素、水杨酸和茉莉酸的质量浓度及其相关基因的表达,BD2231在促进植物生长方面表现更好。

【Objective】This study aims to explore the growth-promoting characteristics and mechanisms of two screened antagonistic bacteria,Bacillus velezensis BD2231 and Streptomyces mirabilis BD2233,so as to provide effective microbial agents for controlling basal rot of hybrid bamboo and enhancing plant growth.【Method】Qualitative and quantitative methods were used to determine the abilities of BD2231 and BD2233 in the secretion of indoleacetic acid,phosphorus solubilization,iron carrier production,biological nitrogen fixation,ACC deaminase production,and cellulase production,and to analyze the effects of the two strains on the germination of tomato and tobacco seeds,as well as on the growth of tomato,tobacco,and hybrid bamboo seedlings.ELISA kits and real-time fluorescence quantitative PCR method were used to investigate the effects of the strains on the concentrations of IAA,GA,SA,and JA and the expression of their related genes in the leaves of tomato,tobacco,and hybrid bamboo.【Result】Both BD2231 and BD2233 were able to produce IAA,iron carrier,and cellulase,but did not have the ability of phosphorus solubilization,biological nitrogen fixation,and ACC deaminase production.BD2233 secreted IAA at a concentration of 12.44 mg·mL^(-1),and BD2231 achieved the carrier activity unit(SU value)of 26.7%and cellulase activity(CMC enzyme activity)of 0.43 U·mL^(-1),respectively.Two strains of biocontrol bacteria significantly promoted the germination of tomato and tobacco seeds,and the germination rates of tomato and tobacco seeds treated with the fermentation broth of strain BD2231were higher,at 61%and 87%,respectively.In addition,the two strains significantly promoted the growth of hybrid bamboo seedlings and increased the plant height,stem thickness,fresh and dry weight.BD2231 and BD2233 significantly promoted the expression of endogenous hormones,such as IAA,GA,SA,and JA,pathway-related genes IAA9,GA20ox,PR-1,and MYC2 in plant leaves and increased the concentration of endogenous hormones.BD2233 was more effective in improving the concentration of IAA,while BD2231 was more effective in increasing the concentration of GA,SA,and JA in plants.【Conclusion】B.velezensis BD2231 and S.mirabilis BD2233 promote plant seed germination and seedling growth through the production of IAA,iron carrier,and cellulase.They can also increase the concentration of IAA,GA,SA,and JA,as well as the expression of their related genes,with BD2231 performing better in promoting plant growth.