Molecular Network-Based Annotation of Saccharomyces cerevisiae and Pachysolen tannophilus Metabolites and Evaluation of Their Bioactive Potential Against Rice Pathogens Magnaporthe oryzae, Bipolaris oryzae and Rhizoctonia solani

This study investigates the biocontrol potential of extracts derived from the liquid co-cultivation of Saccharomyces cerevisiae and Pachysolen tannophilus , as well as from their respective monocultures, using xylose and xylulose as carbon sources, against phytopathogenic fungi affecting rice crops. LC-HRMS analysis, combined with advanced dereplication techniques, led to the annotation of several diketopiperazines, including cyclo(leucylprolyl), cyclo(phenylalanine-4-hydroxyproline), cyclo(prolylvalyl), cyclo(leucylvalyl), cyclo(phenylalanylprolyl), and cyclo(leucyl-4-hydroxyprolyl). The antifungal activity of the extracts was evaluated against Magnaporthe oryzae , Bipolaris oryzae , and Rhizoctonia solani , the causal agents of rice blast, brown spot, and sheath blight, respectively. In vitro assays included dual culture bioassays, assessments of conidial germination, and appressorium formation analysis. The co-culture extract completely inhibited appressorium formation (100%) and reduced conidial germination by 78%, exhibiting a minimum inhibitory concentration (MIC) of 1.25 mg/mL. Additionally, extracts from P. tannophilus at the same concentration showed notable antifungal effects, inhibiting 97.33% of appressorium formation and reducing conidial germination by 83.67% in M. oryzae , underscoring their potential in phytopathogen control. These findings indicate that the bioactive metabolites present in the extracts, particularly the annotated diketopiperazines, offer significant bioactive potential and represent a promising and sustainable alternative to conventional agrochemicals for rice disease management. • Co-culture extract fully inhibited appressorium formation in M. oryzae • P. tannophilus extract reduced conidial germination by 83.67% • LC-HRMS enabled annotation of antifungal diketopiperazines • Biocontrol potential against rice pathogens using xylose/xylulose-based extracts