Identification, Fermentation Parameters Of Strain HG2393 Of Endophytic Actinomycete Isolated From Ginkgo Biloba L. Plant And Its Insecticidal Activities Against The Larvae Of Plutella Xylostella L.

Abundant endophytic actinomycetes were isolated from leaves, stem and root of Ginkgo biloba L. plants collected from Hangzhou, Changxing, and Lin-an, Zhejiang Province. One strain of those endophytic Streptomyces, HG2393, was screened out by monitoring the insecticidal activity against the larvae of Plutella xylostella L. In this paper, its identification, fermentation parameters were studied and the insecticidal activity of the crude extracts of the mycelium was determined. The results are shown as follows.Based on the polyphasic studies including its morphology, physiological and biochemical characteristics, chemotaxonomy and 16S rDNA sequence analysis, and comparison with genus Streptomyces in the utilization of carbon source in Genebank, Strain HG2393 was a new subspecies of genus Streptomyces and named as Streptomyces griseus subsp. hangzhouensis. It grew well on most tested media. The aerial, substrate mycelium and spore were abundant.The effects of medium composition on the insecticidal activities were measured with 8 different mediums. Results indicated that nutrition sources influenced significantly the production of strain HG2393. The highest insecticidal activity was observed on No. 6 medium. By experiments of carbon and nitrogen utilization, strain HG2393 showed more biomass and higher insecticidal activity when maltose and peptone were supplied as carbon and nitrogen sources in the medium, respectively. Meanswhile, higher insecticidal avtivity was observed when the initial pH was adjusted beween 6.5 and 7.5, and the medium volume was 60-80 ml in 300 ml flask at 28℃.Its fermentation process of strain HG2393 could be divided into three phases: the mycelium grows in 0~36 hours, products synthesizes in 48-60 hours and mycelium autolyzes after 72 hours. The insecticidal activities of the crude extracts of...