ABSTRACT

An alternative to controlling weeds resistant to conventional herbicides is the isolation of new active principles. Fungi can produce phytotoxic metabolites that may be used in the development of new herbicides. The objectives of this study were: (1) isolate, select, and identify a fungus producer of phytotoxic metabolites and (2) optimize the culture conditions of this fungus in a low-cost culture medium, with the aim of increasing the phytotoxic effects of their metabolites in weeds and commercial plants. Fungi were isolated from the leaves of Conyza sp. with disease symptoms and selected according to the production of phytotoxic metabolites in solid and submerged fermentation in a low-cost culture medium. A Plackett–Burman Design and Central Composite Rotational Design were used to optimize the conditions of temperature, agitation, pH, and concentrations of glucose and yeast extract in submerged fermentation. The phytotoxic metabolites produced under optimal conditions were tested on 10 commercial plants and weeds that are difficult to control. Of the nine fungi isolated, Mycoleptodiscus indicus UFSM54 produced higher leaf lesions. The production of phytotoxic metabolites was optimized when the fungus was cultivated at 35°C, 50 rpm, and 1.5 g L⁻¹ of glucose in submerged fermentation. The metabolites of M. indicus caused severe phytotoxic effects on germination and seedling growth, and enhanced lesion development on detached plant leaves. The present study is the first to report on the production of phytotoxic metabolites by M. indicus, a potential producer of bioherbicides.

摘要

控制对常规除草剂有抗性的杂草的替代方法是分离新的活性成分。真菌可以产生可用于开发新除草剂的植物毒性代谢物。本研究的目的是：(1) 分离、选择和鉴定产生植物毒性代谢物的真菌；(2) 优化这种真菌在低成本培养基中的培养条件，目的是提高植物毒性作用。它们在杂草和商业植物中的代谢物。从Conyza的叶子中分离出真菌sp。具有疾病症状并根据在低成本培养基中固体和深层发酵中产生的植物毒性代谢物进行选择。Plackett-Burman 设计和中央复合旋转设计用于优化深层发酵中的温度、搅拌、pH 和葡萄糖和酵母提取物浓度的条件。在最佳条件下产生的植物毒性代谢物在 10 种难以控制的商业植物和杂草上进行了测试。在分离的九种真菌中，Mycoleptodiscus indicus UFSM54 产生较高的叶片损伤。当真菌在 35°C、50 rpm 和 1.5 g L ^-1葡萄糖的深层发酵条件下培养时，植物毒性代谢物的生产得到优化。M. indicus的代谢物对萌发和幼苗生长造成严重的植物毒性作用，并促进离体植物叶片的病变发展。本研究首次报道了生物除草剂的潜在生产商M. indicus产生植物毒性代谢物的情况。