Biotic interactions in the rhizosphere help plants acquire scarce resources and are an essential target for improving agricultural sustainability. Yet efforts to improve belowground interactions through agronomic management miss a crucial component: the ability of modern crops to recruit and structure their microbiome may have been altered by domestication and breeding. Selection for high yields in environments with high nutrient inputs may have inadvertently led to changes in the rhizosphere microbiome, such that mechanisms for nutrient acquisition and nutrient use efficiency may have been compromised. The first step to investigate this is to examine the structure and function of the microbiome as a function of plant genotype, with a specific focus on N cycling functional groups. The functional capacity of the rhizosphere microbiome and the benefit to the host plant, as well as ecosystem services such as nutrient cycling and greenhouse gas emissions, vary with the composition and abundance of microbial assemblages. We hypothesized that plant genotypes differ in their ability to recruit microbial functional groups. We used targeted functional metagenomic sequencing to survey the rhizosphere of diverse maize genotypes to compare their capability to recruit microbial nitrogen cycling functional groups, and examined rates of nitrogen transformations among maize genotypes.
Results/Conclusions
Significantly different microbial community structure and N transformation rates were observed as a function of maize genotype. Distinct composition and abundance of N-cycling functional groups were observed among maize genotypes, suggesting that there is genetic capacity to optimize recruitment of N cycling functional groups, and improve crop sustainability. Our observations suggest that limitations in the ability of modern crops to take advantage of environmentally-sound management approaches that rely on cycling of organic matter may be a consequence of the differences in the recruitment of the microbiome, and may explain yield gaps observed in these systems. Our results allow the linkage of host-associated microbial communities and ecosystem function. Understanding this relationship will allow breeders and ecosystem scientists to select crop cultivars that interact with the nitrogen cycle in predictable beneficial ways to improve the efficiency and sustainability of agriculture, while protecting environmental quality.