Manipulating Beneficial Fungal Endophytes for the Protection of Cotton in the Field

Beneficial fungal endophytes have the potential to confer protection to plants from a variety of stressors including nematodes, insects, pathogens and environmental conditions such as drought. In lab and greenhouse assays, specific candidate fungal endophytes can be selectively inoculated into cotton, and when present, reduce the reproductive rates of both root-knot nematodes (Meloidogyne incognita) and cotton aphids (Aphis gossypii).  As a key step in utilizing fungal endophytes for the management of cotton pests, we evaluated the ability to selectively manipulate cotton-endophyte interactions under natural field conditions.  Cotton seeds inoculated with different spore concentrations of two different candidate fungal endophyte species were planted in the field using a replicated, randomized block design.  Endophytic colonization frequencies were high for both species of endophyte based on assays of surface sterilized cotyledons. Cotton inoculated with either of the two candidate endophytes differed from uninoculated control plants in several ways including harbouring fewer aphids, and having higher 1st position square and boll retention levels over the course of the growing season. These results constitute a unique field-scale demonstration of targeted fungal endophyte manipulation in cotton and provide the basis for more thorough evaluations of an expanded range of potentially beneficial fungal endophytes.