摘要:研究玉米||大豆种间互作对根际微生物群落结构的影响及其与产量的关系, 对于深入理解特定作物间套作模式的产量效应有重要理论与实际意义。本研究应用随机区组试验设计方法, 在玉米与大豆以最佳间作比例(2∶3)条件下, 采用无隔(无隔离)、网隔(尼龙网分隔)、全隔(塑料薄膜分隔) 3种种间根系间隔处理, 并以两作物的单作为对照, 借助BIOLOG和T-RFLP技术对不同处理下间作玉米与大豆的根际微生物多样性进行分析, 探究不同种间互作对微生物结构和功能的影响及其与复合作物群体产量的关系。结果表明, 玉米||大豆间作下, 无隔、网隔和全隔的根际土壤阻断处理的土地当量比分别为1.39、1.13和0.98, 同一间作模式下种间根系互作加强, 土地当量比随之提高。进一步分析表明, 无论是间作玉米还是间作大豆, 其根际土壤微生物多样性和均匀度指数均随根系互作加强而明显提高。AWCD分析根际微生物生理种群差异的结果显示, 在玉米与大豆间作体系中, 无隔和网隔处理的根际微生物对底物碳源利用能力分别占据第1和第2位; 全隔和单作下, 根际微生物对底物的利用能力相应降低; 而加强种间根系互作(即从网隔到无隔), 大豆根际微生物对6大类碳源底物中酚类碳源和羧酸类碳源利用能力有所下降, 对胺类碳源、聚合物类碳源、氨基酸类碳源和碳水化合物底物的利用能力分别提高181.01%、32.6%、37.84%和78.28%; 而玉米根际微生物对酚类碳源、聚合物类碳源和氨基酸类利用能力有所下降外, 对羧酸类碳源、碳水化合物类碳源和胺类碳源等底物利用能力分别提高46.26%、6.54%和15.84%。T-RFLP分析结果发现, 与全隔处理比较, 无隔处理的大豆根际红球菌属和喜盐芽孢杆菌属等优势菌群丰度明显增多。而玉米根际微生物中也发现相似生理功能红球菌属和芽孢杆菌属等有益优势菌群的丰度增多现象, 最终导致间作作物地上部产量和土地当量比提高。
关键词:大豆||玉米间作/
种间根系互作/
根际微生物/
细菌/
群落结构/
多样性/
土地当量比
Abstract:Studies on the effects of the interspecific interactions of maize||soybean intercropping on the rhizosphere microbial community structure and their relationship with crop yield are of theoretical and practical significance for elucidating the yield effects of interspecific crops in intercropping systems. The aim of this study was to explore the changes in microbial community structure in the rhizospheres of soybean and maize planted under an intercropping system (soybean||maize) with a 2∶3 line ratio and a randomized design pattern with three types of partitions between two crop roots. The intercropping partitions were a mesh barrier (MB, with exchange of root extudates without roots interaction) or a polythene film barrier (PB, without exchange of root extudates and roots interaction) to separate the maize roots from soybean roots or no barriers (NB) between the roots. An independent monoculture (M) was set up as a control. BIOLOG and terminal restriction fragment length polymorphism (T-RFLP) assays were used to investigate the microbial community diversity in the maize||soybean rhizospheres. The results showed that the land equivalent ratios (LERs) under NB, MB, and PB conditions were 1.39, 1.13, and 0.98, respectively, at a plant row ratio of maize||soybean of 2∶3. These findings suggest that the LER increases with increased interspecific root interactions from PB to NB under the same intercropping pattern. Further analysis revealed that the microbial diversity and evenness indexes in the rhizosphere of both intercropped maize and soybean similarly increased with the increase in interspecific root interactions from PB to NB. Average well color development (AWCD) analysis showed that the rhizospheric microbial communities under NB and MB conditions had the strongest overall ability to utilize carbon sources as substrates, whereas those under PB and M conditions had a lower ability in this regard. The enhancement of interspecific root interactions increased the ability of rhizospheric microbes of intercropped soybean to utilize amines, polymers, amino acids, and carbohydrates (four types of carbon-source substrates) by 181.01%, 32.6%, 37.84%, and 78.28%, respectively. However, the capability of microbes in the intercropped soybean rhizosphere for utilizing two other carbon sources (phenols and carboxylic acids) decreased. Moreover, the ability of the microorganisms in the intercropped maize rhizosphere to utilize carboxylic acids, carbohydrates, and amines increased by 46.26%, 6.54%, and 15.84%, respectively, whereas their ability to utilize phenols, polymers, and amino acids decreased. T-RFLP analysis revealed a significant increase in the abundance of dominant bacteria, such as Rhodococcus (Actinomycetes) and Halobacillus (Firmicutes), in the rhizosphere of intercropped soybean under NB compared with that under PB; whereas the abundance of beneficial dominant bacteria, such as Rhodococcus (Actinomycetes) and Bacillus (Spirochetes), markedly increased in the rhizosphere of intercropped maize under NB conditions compared with that under PB conditions. As a result, the crop yield and LER increased under intercropping conditions.
Key words:Soybean||maize intercropping/
Interspecific root interaction/
Rhizosphere microorganisms/
Bacteria/
Community structure/
Diversity/
Land equivalent ratio
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