Biological Characteristics of Eight Verticillium lecanii and Their Effects on the Pathogenicity against Myzus persicae Aphids

The objectives of this study are to identify the species of fungi collected from naturally diseased Myzus persicae(Sulzer) aphids in the field and to screen the highly virulent strains against M. persicae aphids. After conventional isolation and purification of the collected diseased M. persicae aphids, the strains were used for colony growth, sporulation, morphological observation, ITS sequence analysis, phylogenetic tree construction and indoor toxicity determination. The results showed that:8 strains were isolated systematically from diseased M. persicae aphids which were Verticillium lecanii through identification by biological characteristics, ITS sequence comparison and phylogenetic tree construction. Strain V4 was selected based on biological culture and virulence test. Strain 4 showed more sporulation yields (1.89×10⁹/dish), fast growth rate (reached 68.78 mm at 15 days), batter pathogenicity to M. persicae aphids (7 day corrected mortality was 84.99% and the LT₅₀ was 4.51 d) which has the potential to control the M. persicae aphids continuously in the field.