Fungal endophytes and their potential for biocontrol in cotton

Asymptomatic fungal endophytes can provide protection to plants from a range of biotic and abiotic stressors. Included among these fungal endophytes are several species that are also known to be insect pathogens. Several fungal entomopathogens (e.g., Beauvaria bassiana, Lecanicillium lecanii and Paecilomyces spp.) can be both isolated from and inoculated to live systemically within a broad range of plants. As part of a survey of fungal endophyte diversity in cultivated cotton, we recovered a number of fungal endophytes that are known to act as antagonists against insects, plant pathogens, and nematode pests. In greenhouse trials to investigate effects on insect herbivores, we successfully inoculated cotton seedlings using seed treatments of a field-collected endophytic strain of Paecilomyces sp. and a commercially available strain of Beauveria bassiana.  In both cases, cotton aphid (Aphis gossypii) reproduction was significantly reduced on endophytically-colonized plants versus uninoculated controls. An important consideration for the potential use of fungal endophytes in biological control is the potential for either positively or negatively correlated effects of endophytic colonization on plant performance. We found varying dose-dependent effects of both B. bassiana and Paecilomyces sp. endophytic colonization on total plant biomass, shoot and root length of endophyte-colonized versus uninoculated control cotton seedlings. Results of ongoing replicated field trials testing endophyte inoculation efficiency and protection from insect herbivores will be discussed.