Assessment of Plant Pathogenicity of Endophytic Beauveria bassiana in Bt Transgenic and Non‐Transgenic Corn

Abstract

Field and greenhouse studies were conducted to determine the proclivity of Bacillus thuringiensis (Bt) (Berliner)‐transgenic corn (Zea mays L.) to form an endophytic relationship with Beauveria bassiana, and to evaluate the corn for possible plant pathological effects associated with this relationship. Beauveria bassiana (Balsamo) Vuillemin was applied as a granular formulation to two separate lines of corn, expressing Bt events MON802 and MON810, and their corresponding isolines. There were no significant differences in levels of endophytism between transgenic events or their near‐isolines. In greenhouse studies, B. bassiana was applied as a liquid seed treatment to Bt transgenic corn hybrids Pioneer 34R06 (event MON810) and Ciba Max 454 (event 176) and their near isolines at a rate of 2 × 1010 conidia per ml. There were no significant differences in seed germination or presence of root pathogens in transgenic or isoline seeds soaked in a B. bassiana suspension. The same lines of corn were used in field experiments with treatments of seeds soaked in a suspension of B. bassiana, a foliar application of a granular formulation of B. bassiana, and corresponding untreated checks. Plants were sampled throughout the growing season and evaluated for growth of individual plant components, including sheaths, leaves, stem, husk, ear, plant leaf‐to‐stem ratio and overall plant growth. There were no significant differences in overall plant growth between the B. bassiana treatments or in the growth of each plant component. The results of this study indicate that B. bassiana readily forms an endophytic relationship with transgenic and non‐transgenic corn and causes no plant pathology.

Effect of inoculation method and plant growth medium on endophytic colonization of sorghum by the entomopathogenic fungus Beauveria bassiana

“…Plant growth in vermiculite was much less than in sterile and non-sterile soil, regardless of the inoculation method. Lewis et al (2001) reported no differences in growth between plants treated or not treated with B. bassiana. In the current study, seed treatment with B. bassiana did not reduce seed germination or seedling growth, and did not result in the development of root disease.…”

Entomopathogenic fungal endophytes

“…Nevertheless, in a subsequent paper Bing and Lewis (1992b) report surface-sterilization of tissues and recovery of B. bassiana, thus providing evidence of an endophytic relationship. The possible mode of action for endophytic B. bassiana against O. nubilalis was not discussed in any of these studies or in subsequent studies (Lewis et al, , 2001. The fact that no mycosed insects were reported (except for Bing and Lewis, 1993-see Section 4) suggests that the reduced tunneling reported in all the papers (Lewis and Cossentine, 1986;Lewis and Bing, 1991;Bing and Lewis, 1991;Bing and Lewis, 1992a,b;Lewis et al, 1996) could be a result of feeding deterrence or antibiosis.…”

Ecological compatibility of GM crops and biological control

“…Some entomopathogenic fungi, such as Beauveria bassiana (Bals. ), form a symbiotic relationship with plants and can subsequently infect insects that feed on these plants; B. bassiana appears to establish equally well in maize producing or lacking Cry toxins (Lewis et al, 2001). Taken together, these studies suggest that direct effects of GM crops on entomopathogens are either subtle or absent.…”