Study On Nomuraea Rileyi Cq Strain (Nr-cq0310) From Silkworm In Chongqing China

Nomuraea rileyi (Farlow) Samson is an entomogenous fungus capable of infecting several economically important pests such as Helicoverpa armigera, Spodoptera litura, Trichoplusia ni, and is able to cause desease epizootic in natural environment representing a great potential application in IPM (Integrated Pest Management) system. Studies have been made extensively to the fungus in USA, India but not in our nation. We isolated a strain from infected silkworm (Nr-cq0310 strain), and studied on its morphology, on growth, culture, effects of environmental factors influencing the germination, growth and conidial production and also their infectivity to Spodoptera exigua and mass production. Here below are the results:1. MorphologyConidia, one-celled, ellipsoidal or ovoid, with one blunted end and one subulate end, smooth, often has distinct neck in one end, measuring 3.2-4.6x2.5-3.2μm; Conidiophores, monomematous, erect, -160x3.2-5.1μm, 3-4 verticillate branches, 2-3 phialides on the branch, line or biline. Phialides, bearing apically one to several conidia have swollen base. In view of the extensive observation, we conclude the strain as a kind of Nomuraea rileyi in the genus of Nomuraea, and named it as Nomuraea rileyi cq (Nr-cq0310) strain. Spore germination was seen 24h after culturing in media, most germinating at one side, and also bipolar germination. Vegetative hyphae are sinuous at one side, and a lighter color was seen after the contents of spore were released through the germ tube.2. Solid and liquid cultureThe strain is readily to produce spores, which might be much richer than the strain of Beauveria bassiana. A large quantity of green spores was seen after 7-10days culturing in solid culture, dark green in mass. Small colony with low expansion and exudates-inducing bulge were common to be seen. Spore conidiation was initiated from the center of the colony, and then expanding to the side. Conidia are dry and readily to disperse. Liquid shake culture indicated cluster in conidia and mycelial mass or regiment were produced.3. InfectionYeast-like and podiform and cylindrical-shaped blastospores were the typical characteristic of strain in silkworm. 3-4days postinoculation, short hyphal formations were achieved in hemolymph by microscope inspection. All the three types of blastospores are septate. In the middle of the septum cell, lateral bulges with a cluster of spore content are observed. Infected silkworms with rotiform disease spot, light color in center while dark in outside, more abundant in abdomen. Muddy blood, reduced activity in food taking and movement, tighten body (somewhat hyaline and elasticity) were seen. Under the condition of high relative humility for only (?)day, the white hyphae turned to be...