Development of a novel bioassay for evaluating of the infectivity and between generation transmission effects of entomopathogenic fungi Beauvaria bassiana (Balsamo) Vuilleminon on population of Sawtoo

ABSTRACT: Growth, infectivity and colonization rates of blast spores and conidia of strains IRAN441C of Beauvaria bassiana was assessed against activity of the larval and adult stages and between generation transmission rate of Saw toothed Beetle (Oryzaephilus surinamensis) under three different feeding condition including Sayer, Zahedi and Deiri Date palm Cultivars. Thirty adults and Larvae of beetle were randomly selected and immersed in the fungus suspensions (1000 conidia/ml) for 20s. All assays were rated at 3, 6 and 10 days after treatments. Between generations transmission experiments were designed by divided the studied population into two groups as infected and susceptible individuals. This test was done in factorial completely random design. The fungal development index (FDI) was used to compare the development rating of the fungal strain in the insect hosts. Results showed that The FDI values differ significantly for Date cultivars as feeding condition (F=25.02; DF= 2; ?= 0.01) and for growth larval and adult stages of the insect (F=15.75; DF=5; ?= 0.01). The highest mean of FDI was showed for adult stage fed on Deiri cultivar and the lowest was for larval stage of Zahedi cultivar. The highest between generations transmission ability observed between the populations grew in Deiri and Zahedi cultivars and in the first generation. The mean of the FDI values indicated that the infection, colonization and transmission rates of the B. bassiana in the hosts not only can be affected by the kind of feeding resources of Date cultivars but also can be affected by the host growth stages.