Regulatory effects of winter Morchella esculenta cultivation on the summer maize phyllosphere microbiome and plant health-related traits

In response to the intensifying demand for reduced fertilizer use and increased climate instability, the strategic incorporation of cover crops to improve the maize (Zea mays L.) phyllosphere microenvironment and leaf functional traits has emerged as an important approach for sustaining and enhancing crop productivity. This study compared the effects of two-year (2023–2024) winter cultivation of Morchella esculenta (ME) and fallow (CK) on summer maize leaf functional traits, phyllosphere microbial community composition, and their potential implications for maize health-related traits. The results showed that the interannual variation mainly affected stomatal density (P < 0.05). ME increased net transpiration rate by 30.7% (P < 0.05) and net photosynthetic rate by 23.0% compared to those of CK. ME exhibited varying degrees of enhancement in water-holding capacity and phyllosphere nutrient levels than those for CK, except for vitamin C and inorganic phosphorus content. Consistent with these physiological shifts, the bacterial normalized stochasticity ratio (NST) decreased under ME; meanwhile, β-deviation relative to that of the CK treatment increased, which was accompanied by selective enrichment of putative plant growth-promoting genera such as Glutamicibacter and Microbacterium and inhibition of the potential pathogen Erwinia. By contrast, the fungal NST remained above 50% and further increased under ME, whereas network complexity and the proportion of persistent taxa increased. Overall, ME cover cropping modified carbon–water–defense allocation in maize leaves and altered leaf surface conditions. Bacterial communities exhibited enhanced deterministic assembly coupled with enrichment of growth-promoting taxa, whereas fungal communities were characterized by amplified stochasticity and a more consolidated network structure. Therefore, the cultivation of ME in winter is recommended as an optimal management practice.