Evaluating the effect of Beauveria bassiana on secondary metabolite contents and green peach aphid (Myzus persicae) infestation level on lettuce (Lactuca sativa L.)

Abstract

Endophytic fungus play a crucial role in protecting food crops against phytophagous insects through endophytism. In this greenhouse study, two sets of potted lettuce plants were inoculated with one of four fungal conidial concentrations: 0, 1 × 106 , 1 × 107 , and 1 × 108 conidia mL-1. The first set of plants was used to test the effect of B. bassiana inoculation on aphid infestation levels on lettuce in meshed boxes. The second set of plants was used for assessing the effects of fungal inoculation on secondary metabolite contents. The results showed that the fungus did not significantly (P > 0.05) affect insect infestation levels. However, total polyphenol contents varied significantly with conidial concentrations. The GCMS analysis detected a wide range of volatile compounds, with two well-known insect repellents, 3-octanol and 2,4-di-tert-butyl-phenol, occurring at significantly (P < 0.01) higher concentrations in the fungus-treated plants than the control plants. In conclusion, B. bassiana inoculation significantly enhanced polyphenol content and the quantities of some volatile compounds.