Study For Mass Production, Formulation And Storage Of Entomopathogenic Fungus Dh Strain

Emericella quadriclineata ,Dh strain is entomopathogenic fungus isolated from insect. It is reported that the fungus is far-ranging species in the world, it distributes in the north area in our country. The study was attempted to search for technical approaches to improving mass production of aerial conidia, and prolonging shelf life under normal storage conditions.A modified technology for production of high-quality conidia powder on low-quality rice substrate. Low-quality rice used as solid substrate was tested to produce aerial conidia of Dh strain in 15-cm dishes or large trays. The thickness of rice layer piled in dishes, and the source and concentration of supplemented nitrogen were found affecting conidial yield, viability, and water content. The thinner the rice layer the lower the water content in the conidia powder produced. Adding a very small amount of peptone, KN03 or NH4N03 to the rice substrate significantly increased conidial yield and viability, but there was little difference among the nitrogen sources tested. A supplement of 0.3 KN03 (w/w) was found most favorable to conidial production, In an expanded experiment , the powdery product was in high quality with pureness of 9.61×108 conidia/g, viability of 96.34%, and water content of 28.15%. The results indicate that the low-quality rice can be utilized for efficient production of high-quality B. bassiana conidia for microbial control of insect pests.Physiological changes of stored conidia. In an attempt to examine physiological changes of stored conidia in contents of internally reserved saccharides and proteins and their possible correlation to fluctuating viability, the powders of Dh conidia with water contents of 23.2%,16.0% and 11.3% respectively were preserved at 4℃and 25℃and assayed for viability of the conidia and contents of their saccharides and proteins at 15d intervals during a 150-day period of storage. The contents of the reserved saccharides decreased slowly during the first three months then fluctuated more or less whereas the contents of the reserved proteins tended to decline during whole period of storage though sometimes fluctuated. In the present test, powder of Dh conidia at 4℃saccharides and proteins fluctuated more or less . The viability of the conidia stored at 4℃always declined far more slowly than that at 25℃with greater and faster viability loss occurring in the treatments of higher water contents.Impact of surfactant and pesticide. In testing twelve surfactant, the germination of conidia in Tween-80 and Xi yingmen detergent is higher than others. Inhibition increase with the rise of surfactant concentration, the result showed that surfactant concentration affect conidia germination. In three testing concentration, the impact of 0.05% concentration is the lowest to conidia germination, there was much difference among three concentration. The pesticide has defferent germination to Dh fungus.In summary, the present study contributed to establishing the modified technology for mass production of Dh conidia on nitrogen-supplemented rice substrate. The shelf life under normal conditions could be extended by incorporation such as a control of water content in conidia as low as possible. Entomopathogenic fungus is affected by outside circumstance in the course of using. Surfactant can effectively play down exterior tensility, enhance conidial dispersal in the water. Toxicity of pesticide is calculated for that control function of Dh is fully utilized. Due to a limited period of time for the study, there remain shortcomings left open to further study.