Root exudation processes induce the utilization of microbial-derived components by rhizoplane microbiota under conservation agriculture

Abstract

Root-associated microbiota play an essential role in maintaining the soil-plant-microbial interactions of ecosystems, especially within conservation agriculture systems. However, the effects of conservation agriculture on the plant host, particularly the root system niche, and how it shapes microbiota remains unknown. This study investigated the effects of ridge-furrow plastic film mulch (RFPM), a widely adopted conservation agricultural practice, on root system morphological traits, root exudation processes, the rhizoplane microbiota, and their connections. The results showed that compared with conventional planting, RFPM enhanced root growth, altered root exudate profiles, and changed the rhizoplane microbiota. In particular, root exudation was closely linked to the assembly (relative abundance of bins with a significant phylogenetic signal = 0.17–0.46), structure (explaining 20% of the total variations), and functions (r2 = 0.56–0.73) of the rhizoplane microbiota. It also induced an increase in the proportion of homogeneous selection, with the proportion of deterministic process, which including non-random and niche-based mechanisms, increasing to 46.32% under RFPM; in comparison, the proportion under conventional planting was 40.93%–41.34%. The rhizoplane amino sugar contents under RFPM were 14.33%–31.63% lower than treatments, suggesting the microbial substrate utilization changed according to root exudates, resulting in the utilization of more microbial-derived components. Moreover, the increased amounts of phenolic acids under RFPM coincided with the abundances of microbial type II secretion system and lipopolysaccharide biosynthesis genes. A reconstructed bacterial genome confirmed the existence of microbes that could utilize microbial necromass and phenolic acid. Our results revealed that RFPM causes changes in the rhizoplane microbiota, affecting microbial substrate utilization and physiological adaptation, and highlights the role of root exudation in mediating colonization of rhizoplane-root system niches by the root-associated microbiota in response to conservation agricultural practices.