Endophytic Beauveria bassiana in maize affects survival and fecundity of the aphid Sitobion avenae

Abstract The entomopathogenic fungus Beauveria bassiana is able to colonize and establish a symbiotic relationship with plants as an endophyte, naturally as well as through artificial inoculation. This study aims at implementing a reliable and efficient method to establish endophytic B. bassiana in maize plants. The level of the endophytic establishment was evaluated and the survival and fecundity of the English grain aphid ( Sitobion avenae ) was investigated. Eight-days-old maize plants were sprayed with a fungal spore suspension, while control plants were treated only with a Tween solution. Two weeks after inoculation, seven clip cages per plant, each containing an adult aphid, were attached to different leaves and left for seven days. All inoculated plants contained endophytic B. bassiana as confirmed by plating surface disinfected leaf pieces on selective plates. None of the control plants showed growth of B. bassiana . The highest colonization levels were 61% in older inoculated leaves and 19% in younger non-inoculated leaves. The survival of S. avenae on inoculated plants was reduced up to 49% as compared to control plants. Dead aphids did not show any signs of mycosis. The number of nymphs produced by a single aphid was reduced up to 70% and 74% on inoculated and non-inoculated leaves, respectively. Presence of endophytic B. bassiana in non-inoculated younger leaves implies the movement of the endophyte inside plants. The negative effect on aphid fecundity appears to be systemic as implied by the almost equal reduction of mean numbers of nymphs produced on older and younger leaves on the inoculated plants, irrespective of the level of colonization by endophytic B. bassiana .