การยับยั้งกิจกรรมเอนไซม์ย่อยสลายลิกนินของเชื้อ Ganoderma orbifome เพื่อพัฒนาแนวทางการควบคุมโรคลำต้นเน่าในปาล์มน้ำมัน

Abstract

Oil palm (Elaeis guineensis Jacq.) is an important economic crop in Thailand. One of the problems affecting palm oil production is basal stem rot disease caused by Ganoderma orbiforme (syn. G. boninense). This pathogenic fungus can produce enzymes to degrade lignin, a component of plant cell walls called lignin-degrading enzymes before infection to the host plant. Therefore, this research aims to explain the physical, chemical, and biological factors that affect the activity of lignin-degrading enzymes of G. orbiforme including laccase, lignin peroxidase, and manganese peroxidase under laboratory conditions, and to obtain information for applying physical, chemical, and biological factors to control basal stem rot disease in oil palm. This research was divided into 3 topics; (1.) Condition optimization for enzyme production by G. orbiforme K4/2 under solid-state cultivation. The results found that the optimal solid substrate was oil palm leaves at a solid: liquid ratio of 1:8, incubated at 28 °C for 8 days, and the buffer used for crude enzyme extraction was acetate buffer pH 5.0. (2.) Evaluation of physical, chemical, and biological factors that inhibited the production of lignin-degrading enzymes of G. orbiforme K4/2. It was found that incubation in the dark, the dark alternating with LED light and under blue light, pH 5.0, 6.0, 8.0 and 9.0, addition of nutrients such as Br, Ca, Cu, Fe, Mg, Mn, N, P and Zn, phenolic compounds such as azure B, guaiacol, phenol (concentration of 10–30 mM) and salicylic acid (concentration of 20–30 mM), organic acids such as acetic acid (concentration of 20–80 mM), citric acid (concentration of 20, 60 and 80 mM) and lactic acid (concentrations of 20, 40, and 80 mM) and CaCO3 (concentration of 10–20%), and the used of Trichoderma spp. (Trichoderma sp. Z2-02, Trichoderma sp. Trg3-8, T. asperellum K1-02 and T. asperellum T76-14) could inhibit the lignin-degrading enzyme production by G. orboforme K4/2. (3.) Evaluation of factors that inhibited the activity of lignin-degrading enzymes. The results showed that incubation at temperatures of 60–70 °C, in the dark and the dark alternating LED light, addition of nutrients such as Br, Ca, Cu, Fe, Mg, Mn, N and P, phenolic compounds such as guaiacol and salicylic acid (concentration 10–30 mM) and organic acids such as acetic acid, citric acid, and lactic acid (concentrations of 20–80 mM) inhibited activities of lignin-degrading enzyme of G. orboforme K4/2. The information from this study could be used to develop a manual for controlling basal stem rot disease in oil palm.