Study On The Control Mechanism Of The Endophytic Bacteria Against Colletotorichum Gloeosporioides In Tea Plants

To pormot the current biological control of tea plant diseases and decrease tea pesticide residue, useful endophytic bacteria that can strongly antagonize fungal pathogens such as tea anthrax were separated and screened from tea plant, and the mechanism of disease prevention by endophytic bacteria was explored to provide a theoretical basis on biological control of tea plant diseases. Main tea varieties in Fujian and their sexual progeny were used as experimental materials. The distribution of tea plant endophytic bacteria, screening method of useful endophytic bacteria and prevention mechanisms to tea anthrax were also discussed.1. Lots of endophytic bacteria were found in root, stem and leave of tea tree. The result showed that the amount of endophytic bacteria in different organs was in a positive order as lateral root, taproot, young stem and leave. Moreover significant difference occur in them. The variation coefficient of endophytic bacteria was 70.80% in sexual clone, and 31.90% in asexual clone. Moreover the variation coefficient between different varieties was greater than that in the same varieties. The endophytic bacteria in lateral root and taproot of sexual clones was more than that in asexual clones. However, the endophytic bacteria in young stem and leave of asexual clones was greater than that in sexual clones.2. Through the flat-stand method, 79 strains of endophytic bacteria were isolated and purified from the 5 cultivars (Camellia sinensis cv Huangguanyin, C. sinensis cv Mingke 1, C. sinensis cv Fuding-dahaocha, C. sinensis cv Fuding-dabaicha, C. sinensis cv Fuan-dabaicha), in which 29 strains of tea endophytic bacteria were found to antagonize Colletotorichum gloeosporioides. Moreover, 5 target strains of endophytic bacteria selected from both the healthy leaves of C. sinensis cv Huangguanyin , C. sinensis cv Ming 1 and the young stem of C. sinensis cv Fuandabai had a strong antagonistic effect.3. 5 target strains of endophytic bacteria had a strong inhibitory effect against Colletotorichum gloeosporioides in the indor experiment. The distinct inhibition zone were observed in the flat-stand experiments and the average inhibition rate was 60.09%. The inhibition rate of the strains against Gloeosprium piperatum sporulaction was 72.23%.4. Observed by ordinary optical microscope, the target strains were found to inhibit the mycelial growth of Colletotorichum gloeosporioides, to increase the amount of hyphal branching, and to make hyphal breakdown at the top and the central positions, to enlarge and distort the hypha. Using scanning electron microscopy, it was observed that the cell wall of inhibited hypha of C. gloeosporioides became dry-shrunken, the hyphal end swelled and broke down, the cell content leaked and a large number of cell protoplast spilled, which finally cause the cell disintegration and ablation. Spores of C. gloeosporioides distorted and lost the ability of germination. Using hollow-ground slide culture method, the spore germination rates were found to be significantly reduced by using target strains of endophytic bacteria to deal with C. gloeosporioides conidia, which revealed that tea endophytic bacteria could inhibit the growth of C. gloeosporioides and suppress the germination, formation of the conidia through the secretion of a variety of active substances. Therefore, endophytic bacteria could be used to prevent the infection of C. gloeosporioides to reduce the extent of disease in tea plants.