Identification, Pathogenic Mechanism And Control Of Trichoderma Spp. Isolated From Edible Fungi.

Forty-nine strains of Trichoderma spp.were isolated from 95 samples of spawn and fruiting bodies of edible fungi collected from nineteen regions in Fujian and Zhejiang provinces.The taxonomy,biological characteristics and biocontrol of the strains were investigated,The results were as followes.The morphological characteristics showed that the strains could be divited into four groups,belonging to T.harzianum,T.longibrachiatum,T.atroviride and T. asperellum respectively.The result of ITS analysis was coincident with the morphological classification.The species T.asperellum was first found to contaminate edible fungi,The species,T.atroviride was rarely present,and the frequencies of appearance of species,T.harzianum and T.longibrachiatum were 59%and 31%respectively,seeming to be the dominant contaminative fungi in mushroom cultivation.The species of Trichoderma varied with collective location and mushroom species.The strains isolated from spawn of Lentinula edodes in Qingyuan country of Zhejiang province,were most of the species,T.harzianum.The strains isolated from spawn of Pleurotus eryngii in Guangzhou,were most of the species,T.asperellum,but that isolated from lentinula edodes in Pucheng of Fujian province,were most of the species,T.atroviride.The lengths of the ITS of the tested strains of T.harzianum,T.longibrachiatum, T.atroviride and T.asperellum were 575bp-578bp,579bp-583bp,565bp-567bp and 560bp-561bp,respectively.Their G+C mol%were 55.6%-56.7%,57.2%-58.0%, 55.6%-56.1%and 55.8%-55.9%.The length of 5.8 S of T.spp.was159 bp,and G+C mol%was 46.5%.The forty-nine strains were PCR using five RAPD primers.The results showed that among the strains there was genetic diversity.In the constructed phylogenetic tree,these strains were not clustered according to their geographical origins or hosts. The relationships of interspecies showed in phylogenetic tree were basically consistent with the results of morphological study.The strains of the same species isolated from diferent geographic origins could be clearly distinguished in the tree.Biological characteristics study of Trichoderma spp.showed their growth optimum temperature,water content and pH was 28℃,70%and5.7,respectively. Some of them could grow from 35℃to 40℃,and the lethal pH for mycelia was 11. They could produce conidia easily at high temperatures and under dry conditions, while the mycelia grow well in the wet environments.The infective ability of Trichoderma hyphae to the edible fungi was investigated, the results indicated that different Trichoderma strains displayed different infection ability.It was also found that the fungi Trichoderma had strong infective ability to mushroom but not to phytopathogenic fungi,which also showed that there was infective specificity to Trichoderma towards different fungi.The infective mechanisms of the fungi to mushroom were,that they could infect edible mushroom by lysing or winding the cell walls of mushroom mycelia,or inhibit hyphal growth based on the volatile substances or non-volatile substances generated.However,no direct relationships were proved between the chitinaseoproducing capacity or growth velocity and the invasiveness of the fungi.Inhibitory effects of the fungi Trichoderma could be induced by mushroom mycelia.408 strains of edible fungi were evaluated for the resistance to the fungi Trichoderma.The results indicated 34 strains of Pleurotus ostreatus were resistance to Trichoderma sp No63 by the screening with PDA Plate,but had no resistance to Trichoderma sp No52 with high infective ability by the cultivation re-screening.The results of the screening with PDA Plate also showed that Lentinus edodes,Pleurotus cystidiosus,Grifola frondosa and Pleurotus eryngi were no resistance to the fungi Trichoderma.The results of confrontation culture and anti-bacterial experiment indicated that Bacillus subtilis BS-2 had strong inhibition to the fungi Neurospora,Trichoderma and Mycogone,and could produce the volatile substance to inhibit the germination of the spores of the fungi Trichoderma.By the UV mutagenesis for BS-2,the anti-bacterial activity of the mutant,BS-2-E,increased up to 215%.The substance produced by B. subtilis could be used to control fungal diseases of edible fungi although B.subtilis might cause the pollution of edible fungi cultivation.The lipopeptides produced by B.subtilis included surfactin,iturin and fengycin. Fengycin B and iturin was the main based on the analysis of LC-MS detection of the crude extracts from the fermentation liquids of B.subtilis BS-2 and its two mutants-BS-2-N and BS-2-E.