The Screening Virulent Strain Of Beauveria Bassiana To Laphygma Exigua Hubner And The Study Of Fermentation

Different biological and ecological characteristics, virulence,sporulation,U V radiationviabilities, Protea-Bse activity leve,bathing viabilities and colony growth rates of 9 strainsof Beauveria bassiana were measured respectively. The results were calculated by greyrelational analysis and the optimum sequence was built from the professional comparisonof each strain's characteristics. The BD-B015 strain was determined as the type strain withhighest grey relational indexes.The different strain's virulence titer was calculated bycomparing it's virulence with the type strain's and the BD-B015,BD-B 198 strain showedthe highest titer.In order to estimate the potential of BD-B015 on stream, The strain BD-B015 wasscreened to infect five vegetable insect pests.The result showed that the Laphygma exigua(Hubner), Helicoverpa armigera (Hubner), Plutella xylostella Linnaeus,Pieris rape Linneand Brevicorvyne brassicae(Linnaeus) can be infected by Beauveria bassiana exceptLeucania separata Walker. The death rate of Laphygma exigua (Hubner) was the highest,it's LC₅₀ value was 2.05×10⁶ conidia/mL.The effects of ten chemical pesticides to the mycelium growth and conidiagermination of Beauveria bassiana were tested. The chemical pesticides include sevenpesticides two fungicides and growth hormone.Five concentration were tested,they were1000 mg/L,500 mg/L,250 mg/L,125 mg/L and 62.5 mg/L. The result showed thatfungicides inhibited mycelium growth and conidia germination significantly, with 100%inhibition at the concentration of 1000 mg/L,75% at 62.5 mg/L. And pesticides inhibitedthe strains to a certain degree.Effects of different liquid culture medium on the growth of Beauveria bassiana werestudied with the general sporulation and mycelial substance as an estimate.The resultshowed that the F culture medium was economical and H culture medium on whichBeauveria bassiana grow well and produce big spores, was regarded as a ideal liquidcarrier culture medium. Beauveria bassiana does not grow well and produce bigger sporesexcept F culture medium which contains 4g glucose, 1g yeast extract, 1g peptone, 0.1gK₂HPo₄,0.1g MgSO₄,0.1g Kcl.The optimal fermentative conditions are asfollows:temperature 25～30℃, vibrating time 120～144 hours and not access one third volume as ventilation index. Beauveria bassiana grow well and produce big spores onculture medium which contains complex nutritions such as the F culture medium.The solid compost of Beauveria bassiana was studied. The results showed that thesporulation in liquid culture medium with 30%～40% of the solid media was the best.Andthe quantity of liquid culture medium is differ from different solid compost. In order toreduce the cost and have a excellent effect, the quantity of liquid culture medium should bechoosed before production. Beauveria bassiana grows well on bran without other culturemedium. Put wheat glume or cornstalk flour into bran can depreciate the cost and enlargethe source of solid compost.The result showed that Beauveria bassiana grow well andproduce the most spores on culture medium which contains wheat glume and bran. Theconidia production is 187.69×10⁸/g. Beauveria bassiana can also grow well on residue ofbran after lixiviation in boiled water and its' conidia production is 110.85×10⁸/g.