Fungal and Bacterial Communities Associated with Northern Corn Leaf Blight in Resistant and Susceptible Sweet Corn

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum (Setosphaeria turcica), is a major disease that negatively impacts the yield and quality of sweet corn. Plant-associated microbes hold great potential for enhancing crop productivity and sustainability. This study investigated the fungal and bacterial communities associated with NCLB in resistant and susceptible sweet corn cultivars using amplicon metagenomic sequencing. The structural composition and diversity of the fungal community in symptomatic NCLB-susceptible cultivars differed significantly from those in asymptomatic NCLB-resistant cultivars. In contrast, the bacterial communities showed no significant differences between resistant and susceptible cultivars in both the phyllosphere and rhizosphere. Exserohilum and Alternaria were significantly more abundant in the phyllosphere of symptomatic NCLB-susceptible plants, while fungal genera such as Sporobolomyces and Aureobasidium, along with the order Dothideales and the bacteria Bacillus, were significantly more abundant in the phyllosphere of asymptomatic NCLB-resistant cultivars. Microbial metabolic functions related to sugar metabolism-including sucrose biosynthesis and the degradation of glucose and xylose, compounds abundant in plant cell walls-were enriched in the phyllosphere of symptomatic NCLB-susceptible plants. In contrast, functions associated with detoxification and defense responses to plant phenolic compounds were enriched in microbes from asymptomatic NCLB-resistant cultivars. Additionally, Bacillus, identified ash part of the core microbiome, and the epiphytic yeast Sporobolomyces, identified as a hub in the microbial network, exhibited antimicrobial activity that may suppress E. turcicum. These findings offer valuable insights into the role of microbial communities in plant health and disease resistance, with promising implications for developing microbiome-based strategies to manage NCLB.