Rapid restructuring of rhizosphere and endospheric fungal communities with drought in multiple lines of domesticated sunflower

Plant-associated mycobiomes can influence important host plant traits including those related to disease, nutrient acquisition, phenology, stress tolerance, and productivity. Disentangling the complex multifaceted relationships between host plants and their associated mycobiomes is a critical first step for generating improvements in environmental sustainability and/or plant productivity. Despite decades of work on these plant-fungal interactions, consequences of and mechanisms controlling these interactions are not well resolved, especially in the face of environmental stress such as drought. Moreover, plant differential genotypic responses under stress and associated mycobiome assembly dynamics are likely important in structuring communities but have been less well-studied. We conducted a controlled drought stress experiment by manipulating water treatment in a diverse set of cultivated sunflower lines with different inherent drought resistance levels to evaluate how sunflower host genotypes and drought interacts to affect belowground fungal mycobiomes at the rhizospheric and endospheric levels. Our results demonstrated that fungal community structure was driven by watering treatment, plant genotype, treatment by genotype interactions, genotype by plant compartment interactions and treatment by genotype by compartment interactions. Additionally, our analyses demonstrated the relative abundance of plant pathogens and arbuscular mycorrhizal fungi increased with host genetic variation, or heterozygosity, levels. Our study provides evidence for drought and genotypic drivers of belowground sunflower-fungi interactions and offers a framework for leveraging these interactions to further understand how mycobiome community structure can improve plant productivity under stress.