Assessment of Beauveria bassiana as an endophyte of maize and its effects on plant growth

Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) is an insect pathogenic fungus that is well established as a microbial biopesticide. It occurs naturally in agricultural soil and can grow endophytically (i.e., within plant tissue) in a number of important crops, including maize, Zea mays. However, patterns of colonization of maize tissues by B. bassiana, and effects on growth of maize plants, are not well characterized. We assessed interactions of two strains of B. bassiana with maize. One isolate, GHA, is a well-studied strain and the other, MA20, was brought into culture from an insect cadaver. Maize plants were exposed to B. bassiana by inoculating seeds with fungal conidia prior to planting. This study had three objectives. 1) To test how the presence of B. bassiana affects plant growth. 2) To assess the capacity of B. bassiana to grow endophytically in plant tissues, specifically root, stem and leaf tissue. 3) To measure the persistence of B. bassiana in the growth substrate. We did not detect any significant effects of B. bassiana on growth of maize. However, we did find that inoculating maize seeds with B. bassiana led to endophytic colonization of root, stem and leaf tissues, with the occurrence of B. bassiana colonizing root tissue significantly more than stem and leaf tissue, and stem tissue significantly more than leaf tissue. Additionally, we found evidence for the persistence of B. bassiana in the growth substrate of maize plants. These results provide a better understanding of the interaction of maize with B. bassiana and may aid in the development of approaches to manage pests of maize. In particular, endophytic colonization of plants by B. bassiana can alter interactions of plants with fungal pathogens and insect pests, with research in these areas offering a next step to build on the research described in this study.