2株青贮玉米根际固氮菌的筛选鉴定及促生作用研究

Screening and identification of two strains of nitrogen-fixing bacteria from the silage maize rhizosphere and their roles in plant growth promotion

为了获得优良的固氮菌,并评价其对青贮玉米的促生效果,本研究采用稀释涂布平板法,利用阿须贝氏固体培养基从青贮玉米根际土壤中分离筛选到10株固氮菌,对其固氮能力进行分析,结果表明,菌株ZL-2和ZL^(-1)3的固氮能力较强,菌株ZL-2的固氮量为1.07μg·mL^(-1),ZL^(-1)3的固氮量为0.95μg·mL^(-1)。通过细菌形态学、16S rDNA序列分析和生理生化特征,确定菌株ZL-2为生癌肠杆菌和ZL^(-1)3为成团泛菌。对2株固氮菌的促生特性进行分析,结果表明,2个菌株具有泌铵能力、溶磷能力、产嗜铁素能力和合成吲哚-3-乙酸(IAA)的能力。盆栽试验结果表明,接种固氮菌ZL-2和ZL^(-1)3能够显著提高青贮玉米的株高、根长、地上和地下干、鲜重(P<0.05)。田间试验结果表明,2株固氮菌单接种和双接种均能提高青贮玉米的株高、茎粗、产量、粗蛋白含量和全磷含量(P<0.05)。接种2株固氮菌的青贮玉米,其氮代谢和氨同化相关基因(ZmAMT-4、ZmAMTB、ZmGOGAT2和ZmGS1-3)的表达量显著提高(P<0.05)。因此,2株固氮菌具有较好的促生特性,在提高青贮玉米的产量和品质方面发挥了重要作用,是开发微生物菌剂的优质菌种资源。

The aim of this study was to screen for high-quality nitrogen-fixing bacteria and evaluate their growthpromoting effects on silage maize(Zea mays).The dilution spread plate method with Ashby solid medium was used to screen and screen ten strains of nitrogen-fixing bacteria from the rhizosphere soil of silage maize.The nitrogenfixation capabilities of the strains were analyzed.The results indicated that cultures of ZL-2 and ZL^(-1)3 exhibited strong nitrogen-fixing abilities(1.07 and 0.95μg·mL^(-1),respectively).On the basis of their morphological characteristics,16S rDNA sequence,and physiological and biochemical characteristics,ZL-2 was identified as Enterobacter cancerogenus,and ZL^(-1)3 was identified as Pantoea agglomerans.The growth-promoting characteristics of these two strains were analyzed,and both bacteria were found to secrete ammonium and siderophores,solubilize phosphate,and synthesize indole-3-acetic acid.In a pot experiment,compared with uninoculated silage maize plants,those inoculated with the nitrogen-fixing strains ZL-2 and ZL^(-1)3 showed significantly increased plant height,root length,aboveground and underground dry weights,and fresh weight(P<0.05).In a field experiment,compared with uninoculated silage maize plants,those inoculated with one or both of the nitrogen-fixing strains showed significantly increased plant height,stem diameter,yield,crude protein content,and total phosphorus content(P<0.05).Silage maize plants inoculated with these two nitrogen-fixing strains showed significantly increased expression levels of genes related to nitrogen metabolism and ammonia assimilation(ZmAMT-4,ZmAMTB,ZmGOGAT2,and ZmGS1-3)(P<0.05).Therefore,these two nitrogen-fixing bacterial strains have favorable growth-promoting characteristics.Given their important role in enhancing the yield and quality of silage maize,they are valuable resources for the development of microbial agents.