Differential modulation of α-pyrone production in co-cultures of Pestalotiopsis diospyri with three phytopathogenic fungi

This study investigates the interactions between Pestalotiopsis diospyri and three phytopathogenic fungi— Fusarium guttiforme , Colletotrichum horii , and C. gloeosporioides —isolated from papaya and pineapple. A comparative analysis of metabolite production using 1 H NMR was conducted under axenic and co-culture conditions with rice and potato dextrose broth (PDB) media. Principal Component Analysis (PCA) and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) of the 1 H NMR data revealed metabolic trends between axenic and co-culture conditions, while compound-specific PCA demonstrated distinct species-based metabolite clustering, supporting the observed metabolic changes during interspecies interactions. The results revealed various classes of metabolites in the axenic cultures; however, in the tri-cultures, α-pyrones synthesized exclusively by P. diospyri were differentially expressed, with compounds 11 and 12 showing up to 2-fold increases in yield. The diverse survival strategies exhibited by these fungi, including antagonistic and parasitic behaviors, notably influenced their interactions, leading to the up-regulation and down-regulation of specific metabolites, particularly α-pyrones. Comparative ¹H NMR profiling indicated that the metabolic response to co-culture was dominated by known α-pyrones, with no detectable emergence of uncharacterized metabolites that might signal the production of potent toxins. Furthermore, our findings indicate that the rice medium enhances substrate-fungi interactions, thereby increasing both chemo-diversity and metabolite yield. Preliminary antifungal assays revealed that the α-pyrones exhibited weak to moderate, strain-specific activity against the phytopathogenic fungi, suggesting their ecological role in interspecies competition rather than as potent antimicrobial agents.