黑土农田施加AM菌剂对大豆根际菌群结构的影响

IMPACT OF INOCULATION WITH AM FUNGI ON MICROBIAL COMMUNITY STRUCTURE IN SOYBEAN RHIZOSPHERE IN FARMLAND OF BLACK SOIL

为揭示在黑土农田条件下施加丛枝菌根(AM)菌剂对作物根际微生物群落的影响,试验以大豆为研究对象,田间播种时分别施加根内球囊霉(Glomus intraradices,GI)和摩西球囊霉(Glomus mosseae,GM)两种AM菌剂,以单施化肥处理(F)和不施加AM菌剂及化肥处理(CK)作为对照,采用传统与现代分子生物学手段,研究大豆根际土壤中菌群结构及根系内AM真菌多样性。结果表明:GI、GM处理的大豆菌根侵染率最高达到78.3%和86.6%;GI、GM、F处理的大豆根际土壤中可培养细菌、真菌和放线菌三大菌群的数量与CK处理相比显著提高(p<0.05)。分离大豆结荚期根际土壤中AM真菌孢子,共获得Acaulospora属真菌3种,Glomus属真菌7种,孢子密度均较低,G.intraradices和G.mosseae均为各自处理的优势种群。对大豆结荚期根系和根际土壤PCR-DGGE图谱条带的丰度及优势条带测序分析,结果表明根际土壤中的AM真菌菌群数明显高于根系中AM真菌的菌群数量,GI处理的大豆根际土壤中AM真菌丰度值最大,GM处理大豆根系里的AM真菌丰度值最大,F处理的根际土壤中总AM真菌的数量最少;施加AM菌剂处理的大豆根系及根际土壤中的优势菌群分别为外源施加的两种AM真菌。

To explore impact of inoculation with arbuscular mycorrhizal （AM） fungi on microbial community struc- ture in soybean rhizosphere, a field experiment was carried out using soybean as object of the study. Two different strains of AM fungi, Glomus intraradices （GI） and Glomus mosseae （GM）, were inoculated into the experiment field with soybean seeds in Treatments GI and GM, respectively, and not in Treatments F （fertilized only） and CK （neither fertilized nor inoculated） as control for comparison. Traditional and modern molecular biological approaches were employed to inves- tigate microbial community structure in the rhizospherel and AM fungi diversity in the root system of the soybean. Results show that both the two strains of AM fungi could colonize soybean roots, forming mycorrhizal symbionts in the field, with colonization rate reaching 78.3% and 86. 6% in Treatments GI and GM, respectively, and 15.3% and 16.0% in Treat- ments F and CK, respectively, which indicates that indigenous AM fungi can also form myeorrhizal symbionts in the field, but their colonization rates were much lower. Analysis using the dilution-plate method of community structure of eulturable microbes in the soybean rhizosphere revealed that Treatments GI, GM and F all significantly elevated the abundance of the three soil microbiota： bacteria, fungi and actinomyces, as compared with CK （p 〈0.05）. The effect was the highest onbacteria and actinomyces in Treatment F and on fungi in Treatment GM. Besides, the wet sieve decantation and sucrose centrifugation method was used to isolate AM fungal spores from the rhizospheric soil samples collected at the pod-setting stage of soybean. As a result, 3 species in Acaulospora genus and 7 in Glomus genus were obtained, with G. intraradiees and G. mosseae being the dominant species, separately, in the genera and they were all quite low in spere density. Aher- wards, PCR-DGGE was carried out, to explore band abundance and sequence dominant bands of the PCR-DGGE profiles in the root system and rhizospheric soil of soybean at the pod-setting stage. Molecular detection shows that the population of AM fungi was remarkably higher in the soybean rhizospheric soil than in the soybean root system, and the abundance of AM fungi was the highest in the soybean root system of Treatment GM, while the population of AM fungi in soil was the lowest in Treatment F. In Treatments GI and GM, the dominant fungus species in both soybean root system and rhizospheric soil were the inoculated exogenous AM fungi, which demonstrates the effectiveness and feasibility of application of AM inoculants, The findings of this study has supplied some basic data for promotion of the application of AM fungi inoculant in the field.