Key microbes in wheat maize rotation present better promoting wheat yield effect in a variety of crop rotation systems

Rotational cropping is an important and effective agricultural management practice that significantly contributes to crop yields, plant health, and soil structure. Microorganisms invariably accompany crop growth and play a vital role in facilitating plant nutrient uptake, disease resistance, and adaptation to environmental stressors. Given the essentiality of microorganisms in the soil ecosystem, exploring the contribution of soil microbial communities to the rotational cropping system is of significant reference value for improving the rotational cropping system. Although numerous studies have investigated the differences in microbial communities in various crop rotation systems, considering the factors such as the growth stage of wheat, climate, soil fertility, and human activities that exert a significant impact on soil microorganisms, it is imperative to study the effects of different crop rotation systems on soil microbial communities at various growth stages of wheat under controlled experimental conditions. Based on a 12-year long-term rotational cropping platform, we analyzed the composition and structure of bacterial and fungal communities in the rhizosphere of wheat under three crop rotation systems at four growth stages: wheat-maize, wheat-soybean, and wheat-cotton, and constructed a co-occurrence network to identify potential key functional microorganisms. The results showed that both the rotational cropping system and the growth stage of wheat had significant effects on the microbial communities in the long-term rotational cropping system, while the effects of crop rotation systems (R²=0.140) were stronger than growth stage (R²=0.108). And the differences in microbial communities had a certain cumulative effect on the growth and development of wheat. In addition, the rhizosphere microbial co-occurrence network of the wheat-cotton rotational cropping system had 26 key functional microorganisms, much more than those in the other two systems. However, it is worth noting that the key microorganisms in the wheat corn rotation system have a stronger promoting effect on wheat growth. Two of the key functional microorganisms, Niabella_Hub9 and Dokdonella_Hub24, had a significant promoting effect on wheat yield. This study improves the understanding and recognition of the functions and roles of microorganisms in different crop rotation systems, providing a basis for rational utilization and optimization of crop rotation systems.