Abstract:

The phyllosphere， as a habitat for microorganisms， exhibits a close association between fungal community dynamics and the physiological regulatory network of host plants. This study focused on Atraphaxis bracteata， a common sand-fixing plant in the vegetation restoration area of the southeastern Tengger Desert. By integrating high-throughput sequencing and plant physiological indicator measurements， we systematically analyzed the ecological characteristics of epiphytic and endophytic fungal communities in healthy and diseased plants， and revealed their correlations with host plant carbon-nitrogen-phosphorus metabolism and defense systems. In diseased plants， the pathogenic genus Botryosphaeria significantly increased in endophytic fungi （56.00% vs. 5.41% in healthy plants）， while the symbiotic yeast Kodamaea sharply declined （38.48%→0.50%）. Epiphytic fungal communities exhibited lower Shannon diversity （2.12 vs.2.87） but higher Chao1 richness （286 vs.198 OTUs）， with significant β-diversity differences （ANOSIM R=0.642）. At the host plant level， diseased leaves showed a 15.3% increase in carbon content （P=0.007）， but nitrogen and phosphorus decreased by 12.8% and 30.1%， respectively， alongside suppressed SOD activity （-54.3%） and antagonistic defense responses involving lignin （+45.2%） and salicylic acid （+2.5%）. Fungal-host interaction analysis further indicated that Botryosphaeria abundance strongly negatively correlated with SOD activity but positively correlated with lignin accumulation， suggesting that the pathogen may exacerbate host pathology by disrupting antioxidant systems and activating specific defense pathways. This study provides the first systematic elucidation of the "diversity-function-metabolism" coupling mechanism in desert plant phyllosphere microbiomes under pathogen stress， offering a theoretical framework for microbial-based early warning of vegetation diseases in ecologically fragile regions.

Key words: fungal disease, fungal community, resistance indicators, nutrient elements