Study On Stem Blight Disease And Its Bio-control In Schizonepeta Tenuifolia

Stem blight is one of the most serious diseases of S. tenuifolia. In this study, the pathogen of stem blight disease was isolated and identify as P. nicotianae. Then, based on the results of its biological characteristics research, three Trichorderma strains showing high-antagonistic activity against pathogen were identified, which were T. viride Tv04-2, M3 and T. harzianum ThB. Finally. Furthermore, studies were carried out on antagonistic mechanisms and their biocontrol efficiency in field against stem blight disease of S. tenuifolia. Results were shown as following:1. Samples were collected and the pathogen of stem blight disease was isolated from diseased tissue of S. tenuifolia and then cultured on V8 madium. Based on morphological characteristics, rDNA-ITS analysis and pathogenicity test, which was identified as P. nicotianae.2. Biological characteristics of P. nicotianae were studied. Results showed that, the optimum culturing condition of the pathogen were 25℃, pH7, and a daily cycle of 12 hours of light and 12 hours of dark.3. By antagonistic test method, T. viride TV04-2, M3 and T. harzianum ThB out of 16 candidate Trichoderma strains were identified having highly antagonistic activity against P. nicotianae of S. tenuifolia, and the inhibition rate of them against the pathogen were 83.2%,78.2% and 65.0%, respectively.4. Antagonistic mechanisms of T. viride M3, Tv04-2 and T. harzianum ThB against the pathogen were studied by dual-culture method. Results showed that, T. viride M3 having the highestβ-1,3-glucanases activity, and T. harzianum ThB having the highest proteases activity. Also we found that, they could produce volatile and involatile substances, which having inhibiting activity on the growth of the pathogen. The antagonistic mechanism of Trichoderma spp. against P. nicotianae is including competitive, mycoparasitism and antagonism, etc.5. Evaluation of the biocontrol efficiency of Trichoderma spp. against stem blight disease was carried out in field. Results showed that, controlling efficiency of T. viride M3 was higher than T. harzianum ThB and T. viride Tv04-2 significantly, and which can be used to develop commercial bio-control agent to alleviate the occurence and damage of stem blight disease of S. tenuifolia in field.