Studies On Screening Agricultral Antibiotics From Endophytes In Celastrus Angulatus

Endophytes, including fungus, actinomycetes and bacteria, are the microorganisms that colonize living, internal tissues of plants without causing any immediate, overt negative effects. Some endophytes prouducing agricultural metabolites had been isolated. The aims of this study are to isolate endophytic fungus and actinomycetes from Celastrus angulatus and screen the strains that produce agricultural antibiotics, then the work about the isolation and identification of active components have been carried out. The main results are as follows: Taking different separating culture medium and isolating methods, 68 strains of endophytic fungus and 13 strains of actinomycetes were separated from the bark, phloem and xylem of the roots and stalks of Celastrus angulatus.The insecticidal bioassay results showed that at the concentration of 5%, the acetone extract of the endophytic fungus Hd3 strain mycelium had a mortality of 100% against he 1st instar larvae of Mythimna separata. By means of mycelium growth rate, the fermentation products of 81 strains were tested against Botrytis cirerea, Alternaria solani, Fusarium graminearum, Colletotrichum gloeosporioides, Exserohilum turcicum, Alternaria longipes and Rhizoctonia cerealis. The results indicated that the fermentation products of 5 strains, which numbered A10, 2C2, a4, a5 and c4, had a certain degree fungicidial activity. The results of pot test indicated that the culture of the 5 strains exhibited more than 65% protective efficacy against Blumeria graminis disease. The culture filters of a4 and c4 strains exhibited a certain protective efficacy against Pseudoperonospora cubensis disease. Two compounds (H4.5, H4.6) of insecticidal activity were isolated from the ethyl acetate extracts of the mycelium of strain Hd3 by bioassay-guided. On the basis of spectral technology (1HNMR, 13CNMR, COSY), the structure of H4.5 was identified as 2,3-dimethoxy-5-methyl phenol, which was isolated from microbes for the first time, and its activity was carried out at first. The bioassay results showed H4.5 exhibited strong stomach poison activity against the 3rd instars larvae of Mythimna separata Walker, and the value of LD50 was 3.78μg/larvae. By means of observation on aerial mycelium, macroconidia, microconidia and colony morphology characteristics and comprised with related classify system, strain Hd3 was identified as Aspergillus　sp..