Biological Control On Heterobasidion Parviporum And Its Decay In China

Conifer root and butt rot caused by Heterobasidion spp. is one of the most destructive diseases of conifers in the northern hemisphere. The disease causes significant economic losses with the death of conifer trees. The disease is rather common in the coniferous forests of northeast, northwest and southwest of China. Phlebiopsis gigantea is the best antagonistic fungus to prevent the disease. In order to screen the most effective strain,16strains of P. gigantea were tested for growth rate, competitive abilities on agar medium and the efficacy of control against Heterobasidion parviporum in the stem pieces of Picea jezoenensis. Meanwhile, the activities of extracellular cellulose of P. gigantea was also tested for enhancing accuracy of the research. The present report is the first study on biocontrol conifer root and butt rot in China.Fourteen Finnish and two Chinese P. gigantea strains were used for testing the growth rate and capacity against the Chinese H. parviporum on agar medium. Three strains (04052,08076and08077) with high growth rate and capacity against H. parviporum were selected for further testing in field. The three strains were tested for the efficacy of control against H. parviporum in the stem pieces of Picea jezoenensis. The results revealed that the pre-treated stumps by P.g08077had the least infected area in stumps than untreated one. It indicated that P.g08077had the best capacity on controlling H. parviporum in China.The activities of extracellular cellulase could be used for screening the effective biocontrol strain. So the cellulase activity of P. gigantea was used for a indicator of the fungus for controlling conifer root and butt. Based on single factor and orthogonal experiment, the optimum medium compositions for the highest cellulase activity were (g/L):glucose30.00, peptone5.00, KH2PO43.00, MgSO4.7H2O1.50, the optimal liquid medium volume was120mL/250mL, the optimal inoculum volume was5%(V/V), initial pH4.0. By determining cellulase activity of P. gigantea isolates, P. gigantea08077was found to have the highest cellulase activity. So P. gigantea08077was better than the Finnnish commencial Rotstop to control the conifer root and butt disease in China.