The Relationship Between Activities Of β-1,3-Glucanase And Resistance To Phytophthora Root Rot Of Soybean

β-1,3-glucanase was an important pathogen-related protein. It could catalyze the hydrolysis ofβ-1,3-glucan that was one of the major components of most pathogenic fungal cell walls, which made cell inclusion overflow and dead at last.β-1,3-glucanase can be induced by many biofactors and nonbiofactors.β-1,3-glucanase can hydrolyzeβ-1,3-glucan andβ-1,3-1,6-glucan of fungal cell walls, and the degrading products are a source of elicitors for plant systematic defense response. It not only inhibited the growth of fungal mycelium but also released evocator of fungal cell walls which indirectly promoted to accumulate phytoalexin in host and enhance resistance. Meanwhile, in the light of fewβ-1,3-glucan in plant cell walls, this enzyme would play important roles in resistance to fungal diseases.In this study, the relationship betweenβ-1,3-glucanase and the resistance of Phytophthora root rot of soybean, as well as enzyme properties and antifungal activity ofβ-1,3-glucanase were reported. The major results are as follows:1.β-1,3-glucanase activity were significantly increased after inoculated. After inoculating true leaves,β-1,3-glucanase activity of resistant varieties reached the peak at 48 hour and increased percentage of 105, but middle susceptible and susceptible varieties reached the peak at 72 hour and increased percentage of 67 and 65. It is similar to soybean trifoliolate leaves and true leaves. The relationship betweenβ-1,3-glucanase activities and the resistance of soybean varieties were positive correlation, the peak of enzyme-activity appeared earlier in the resistant varieties than the susceptible ones, and the former have a high percentage of enzyme-activity changes and the time of keeping high activity of these enzymes were longer than latter.2. This study focused on the properties ofβ-1,3-glucanase. The results showed that the optimal temperature and pH of the enzyme activity were 55℃and 5.0, respectively. The enzyme was stable at pH 4.5-6.5 and temperature below 55℃. Theβ-1,3-glucanase activity was inhibited by Mg²⁺,Cu²⁺,Zn²⁺,Fe³⁺,Hg²⁺,Ba²⁺ and stimulated by Ca²⁺,K+,Al³⁺. By Michaelis-Mente′s kinetics assay, The Km and Vm were 0.736 mg /ml and 0.261 mg /(mL·min), respectively.3. The bioassay of antifungal activity showed that the crude enzyme significantly suppressed mycelial growth and conidia germination of Phytophthora sojae.