The plant pathogen Fusarium graminearum is a proficient producer of mycotoxins and other in part still unknown secondary metabolites, some of which might act as virulence factors on wheat. The PKS15 gene is expressed only in planta, so far hampering the identification of an associated metabolite. Here we combined the activation of silent gene clusters by chromatin manipulation (kmt6) with blocking the metabolic flow into the competing biosynthesis of the two major mycotoxins deoxynivalenol and zearalenone. Using an untargeted metabolomics approach, two closely related metabolites were found in triple mutants (kmt6 tri5 pks4,13) deficient in production of the major mycotoxins deoxynivalenol and zearalenone, but not in strains with an additional deletion in PKS15 (kmt6 tri5 pks4,13 pks15). Characterization of the metabolites, by LC-HRMS/MS in combination with a stable isotope-assisted tracer approach, revealed that they are likely hybrid polyketides comprising a polyketide part consisting of malonate-derived acetate units and a structurally deviating part. We propose the names gramiketide A and B for the two metabolites. In a biological experiment, both gramiketides were formed during infection of wheat ears with wild-type but not with pks15 mutants. The formation of the two gramiketides during infection correlated with that of the well-known virulence factor deoxynivalenol, suggesting that they might play a role in virulence.

The objectives of this research was to evaluate the effectiveness of the combination of plant crude extracts and yeasts as an alternative to replace the synthetic fungicide to control green mould rot caused by Penicillium digitatum on citrus fruit. This pathogen caused 90% of citrus losses during the storage. Control of this pathogen mainly with chemicals, but concerned with environmental contamination, human health, and pathogen resistance, chemical treatment is frequently decreased. Eugenia caryophylata crude extracts and Candica utilis showed to be the best combination to attain a reduction in green mould incidence by 90.3% and disease severity by 96.26%. Furthermore, the combination of E. caryophylata crude extracts and C. utilis had a more potent antifungal activity than imazalil. The effectiveness of the combination of plant crude extractss and yeasts can be an alternative treatment to replace the synthetic fungicide to control P.digitatum on citrus fruit, but the application in the packaging line needs further investigation.

Importance of the Work: Sustainable forage production was enhanced by addressing the limited data on microbial bioproduct effects in Napier grass cultivation. Objectives: To evaluate the effects of Bacillus and Trichoderma bioproducts on Napier grass growth, nutrient uptake and physiological responses. Materials and Methods: Two Napier grass cultivars were treated under greenhouse conditions with powdered Bacillus or liquid T. asperellum formulations. Growth parameters, nutrient content, chlorophyll, enzyme activities and indole-3-acetic acid (IAA) content were measured. Treatments were applied at varying frequencies and concentrations, with statistical analyses performed based on analysis of variance and t tests. Results: The microbial bioproducts significantly (p < 0.05) enhanced the growth and physiological performance of Napier grass under greenhouse conditions. Bacillus and Trichoderma increased plant height and leaf number, with responses varying by cultivar and plant age. Bacillus improved the chlorophyll content, particularly in Pak Chong 1, while Trichoderma consistently promoted leaf development. Fresh biomass gains were significant only in the Taiwan treated with Bacillus. The enzyme activity analysis confirmed that Trichoderma stimulated β-1,3-glucanase and peroxidase, whereas Bacillus elevated IAA, indicating distinct microbial effects on plant physiology. Main Finding: Microbial bioproducts, particularly Bacillus and T. asperellum, improved the growth and physiology of Napier grass in a cultivar-specific manner, with Bacillus enhancing the chlorophyll and IAA contents and Trichoderma stimulating β-1,3-glucanase and peroxidase activities.

Chiang Mai Journal of Science, Faculty of Science, Chiang Mai University