Decomposing cover crops modify composition and functioning of root microbiomes of cash crop seedlings

Root microbiome assembly during the seedling stage is of strong importance for subsequent performance of crops. Sowing of crops is increasingly done in soils that contain incorporated residues of cover crops. Here, we report the first extensive study of effects of decomposing cover crop residue on assembly of root microbiomes of cash crops seedlings. We studied bacterial (16S rDNA) and fungal (ITS2) community assembly in roots of four cash crop seedlings (asparagus, carrot, onion, and sugar beet) exposed to residues of seven cover crops species collected from field plots at two harvest times (autumn and winter). Within the context of cash crop species specific selection, we found significant effects of cover crop quality (measured with harvest time) and cover crop species identity on the composition of root-associated microbial communities. In addition, we show that there are significant correlations between cover crop induced shifts in root microbial taxa and disease tolerance of sugar beet seedlings against the pathogenic fungus Rhizoctonia solani. Our results show that incorporation of cover crops presents a possibility to steer composition and improve functioning of cash crop root microbiomes.

作物苗期的根系微生物组组装，对作物后续生长表现具有至关重要的意义。当前作物播种愈发多地在含有翻压还田覆盖作物残体的土壤中进行。本研究首次开展全面系统的探究，分析分解态覆盖作物残体对经济作物苗期根系微生物组组装的影响。我们针对4种经济作物苗期（芦笋、胡萝卜、洋葱、甜菜）的根系细菌（16S rDNA）与真菌（ITS2）群落组装情况展开研究，供试土壤中的覆盖作物残体采自7个覆盖作物物种在两个收获时期（秋季、冬季）的田间样地。在经济作物物种特异性筛选的背景下，我们发现覆盖作物品质（以收获时期表征）与覆盖作物物种属性，均对根系附属微生物群落的组成存在显著影响。此外，我们还发现覆盖作物诱导的根系微生物类群变化，与甜菜苗期针对病原真菌立枯丝核菌（Rhizoctonia solani）的病害耐受性存在显著相关性。本研究结果表明，翻压覆盖作物残体可实现对经济作物根系微生物组组成的定向调控，并改善其功能。