Evaluation of developing maize microbiomes and associations among nitrogen cyclers and key fungal taxa

More sustainable approaches to agriculture are urgently needed to protect existing resources and optimize crop yields and to provide food for a growing global human population. More sustainable agricultural practices that utilize plant-microbe relationships across cultivation are urgently needed. The main objectives of this study were to track the prokaryotic and fungal microbiomes associated with key growth stages of developing maize to evaluate the relationships among nitrogen cycling bacteria and major fungal genera including those known to contain arbuscular mycorrhizal fungi and other important taxa. Prokaryotic and fungal microbiomes associated with bulk soils, rhizosphere soils and tissues of developing maize were characterized using Illumina MiSeq sequencing. Similarities in microbiome diversity and abundance were compared to sample metadata to explore the influence of external factors on microbiome development. Correlations among target fungal taxa, bulk bacteria and nitrogen cycling bacteria were determined using non-parametric Spearman correlations. Important maize-associated fungal taxa were detected in all samples across growth stages, with Fusarium, Penicillium and Aspergillus fungi comprising up to 4.21, 4.26 and 0.28% of all fungal genera, respectively. Thirteen statistically significant correlations between nitrogen cycling genera and targeted fungal genera were also identified (r_S≥0.70 or r_S≤-0.70; P<0.05). This study is the first to note a strong positive association among several nitrifying bacteria and Fusarium (R=0.71; P=0.0046), Aspergillus (R=0.71; P=0.0055) and Cladosporium spcies (R=0.74; P=0.0038), suggesting the levels of soil nitrate, nitrite or nitrification intermediates may have large roles in the proliferation of important maize-associated fungi.