高粱根际高亲和性解磷复合菌系的构建及溶磷、促生效果

Construction of high⁃affinity phosphate⁃solubilizing microbial consortia in sorghum rhizosphere and their phosphate solubilization and growth promoting effects

[目的]本文旨在构建既可在高粱根际高效定殖,又可显著强化单菌株溶磷、产吲哚⁃3⁃乙酸(IAA)能力的复合菌系,提高土壤中难溶性磷利用率,实现高粱节磷栽培。[方法]采用抗生素标记、Salkowski比色法、田间灌根试验、室内液态发酵试验和响应面CCD设计相结合的方法,对可在高粱根际高效定殖、促生效果明显的解磷细菌进行鉴选,并在此基础上构建复合菌系并测定其对高粱栽培的磷肥减施效果。[结果]菌株gz4⁃1、gz2⁃2、1⁃1和1⁃3可在主推高粱品种(晋杂22号、晋糯3号和晋杂2001号)根际高效定殖,灌根处理20 d后活菌数量均可达4.00×10^(5)cfu·g^(-1),同初始接种浓度1.00×10^(5)cfu·mL^(-1)相比活菌数量呈现增加趋势;4菌株产IAA能力以gz4⁃1、gz2⁃2、1⁃1较优,均高于20 mg·L^(-1);发酵72 h菌株1⁃3发酵液中的IAA浓度虽然低于菌株gz4⁃1、gz2⁃2、1⁃1,但仍达9.12 mg·L^(-1),且促生效果明显;复合菌系中菌株gz4⁃1、gz2⁃2、1⁃1和1⁃3的较优起始发酵浓度配比为8.75×10^(3)、1.33×10^(3)、1.00×10^(3)和9.90×10^(3)cfu·mL^(-1),且发酵72 h的溶磷和产IAA能力同单菌株相比显著提升(P<0.05);相同复合菌系接种浓度下和相同施磷水平下,复合菌系促生效果均随施磷量的增加或接种浓度增加呈现先升高后下降趋势,且高粱地上、地下表型指标普遍以接种量为1.00×10^(8)cfu·mL^(-1)时效果较优。[结论]菌株gz4⁃1、gz2⁃2、1⁃1和1⁃3联合发酵形成的复合菌系在接种浓度为1.00×10^(8)cfu·mL^(-1)时可使高粱栽培当季减磷1/4~1/3,对高粱节磷栽培具有重要意义。

[Objective]The aim of this study was to construct a microbial consortium that could efficiently colonize the sorghum rhizosphere and significantly enhance the phosphate-solubilizing and Indole-3-acetic acid(IAA)production capabilities of single strains,thus increasing the utilization of insoluble phosphate in the soil and achieving phosphate-saving cultivation of sorghum.[Method]A combination of antibiotic labeling,Salkowski colorimetry,field root irrigation tests,indoor liquid fermentation ex-periments,and response surface CCD design was used to select phosphate-solubilizing bacteria that could efficiently colonize the rhizosphere of major sorghum varieties,and construct a microbial consortium based on this and determine its effects on re-ducing phosphate fertilizer application in sorghum cultivation.[Results]Strains gz4-1,gz2-2,1-1,and 1-3 could effectively col-onize the rhizosphere of the main sorghum varieties(Jinza 22,jinnuo 3,and Jinza 2001),and after 20 days of root irrigation,the viable cell counts could all reach 0.4×10^(6)cfu·g^(-1),showing an increasing trend compared to the initial inoculum concentra-tion of 1.0×10^(5)cfu·mL^(-1).The four strains all exhibited phosphate-solubilizing capabilities,with gz4-1,gz2-2,and 1-1 being superior,all exceeding 20 mg·L^(-1).Although the IAA concentration in the fermentation broth of strain1-3 was lower than that of strains gz4-1,gz2-2,and 1-1,it still reached 9.12 mg·L^(-1)with a significant growth-promoting effect.In the microbial consor-tium,the optimal initial fermentation concentrations for strains gz4-1,gz2-2,1-1,and 1-3 were 8.75×10^(3),1.33×10^(3),1.0×10^(3),and 0.99×10^(3)cfu·mL^(-1),respectively,and their phosphate solubilization and IAA production capabilities were significant-ly enhanced(P<0.05)compared to single strains after 72 h of fermentation.Under the same concentration of microbial consor-tium inoculation and the same phosphorus application level,the growth-promoting effect of the microbial consortium increased initially and then decreased with increasing phosphate application or inoculation concentration,and sorghum above-ground and below-ground phenotypic indicators generally showed better results when the inoculation concentration was 1.0×10^(8)cfu·mL^(-1).[Conclusion]The microbial consortium formed by strains gz4-1,gz2-2,1-1 and 1-3 can reduce phosphate application by 1/4 to 1/3 for sorghum cultivation in the current season when inoculated at a concentration of 1.0×10^(8)cfu·mL^(-1),which was of great significance for phosphorus-saving cultivation of sorghum.