Detection of the Entomopathogenic Fungus Beauveria bassiana in the Rhizosphere of Wound-Stressed Zea mays Plants

Abstract

Entomopathogenic fungi from the genus Beauveria (Vuillemin) play an important role in controlling insect populations and have been increasingly utilized for the biological control of insect pests. Various studies have reported that Beauveria bassiana (Bals.), Vuill. also has the ability to colonize a broad range of plant hosts as endophytes without causing disease but while still maintaining the capacity to infect insects. Beauveria is often applied as an inundative spore application, but little research has considered how plant colonization may alter the ability to persist in the environment. The aim of this study was to investigate potential interactions between B. bassiana and Zea mays L. (maize) in the rhizosphere following inoculation, in order to understand the factors that may affect environmental persistence of the fungi. The hypothesis was that different isolates of B. bassiana have the ability to colonize maize roots and/or rhizosphere soil, resulting in effects to the plant microbiome. To test this hypothesis, a two-step nested PCR protocol was developed to find and amplify Beauveria in planta or in soil; based on the translation elongation factor 1-alpha (ef1α) gene. The nested protocol was also designed to enable Beauveria species differentiation by sequence analysis. The impact of three selected B. bassiana isolates applied topically to roots on the rhizosphere soil community structure and function were consequently assessed using denaturing gradient gel electrophoresis (DGGE) and MicroRespTM techniques. The microbial community structure and function were not significantly affected by the presence of the isolates, however, retention of the inocula in the rhizosphere at 30 days after inoculation was enhanced when plants were subjected to intensive wounding of foliage to crudely simulate herbivory. The plant defense response likely changed under wound stress resulting in the apparent recruitment of Beauveria in the rhizosphere, which may be an indirect defensive strategy against herbivory and/or the result of induced systemic susceptibility in maize enabling plant colonization.

Endophytic fungi, Beauveria bassiana and Metarhizium anisopliae, confer control of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), in two tomato varieties

“…Similarly, it was demonstrated that BbC1-inoculated Matina and Harzfeuer tomato plants displayed reduced growth effects as a result of infestation with the fall armyworm (unpublished report). Most probably, Bb acted as an antagonist against S. frugiperda larvae by producing metabolites that reduced insect infestations on their host plants (Jaber and Ownley 2018) or changed the plant defense responses and recruited Bb as a defensive strategy against insect herbivore (McKinnon et al 2018).…”

Root colonization by endophytic insect‐pathogenic fungi

“…The persistence of Beauveria inoculum in the rhizosphere of corn after 30 days was enhanced when plants were subjected to intensive wounding of foliage which crudely simulated herbivory. This was explained as a defence against insect herbivory that also has the result of promoting Beauveria colonization in the plant (McKinnon et al 68).…”

Meta-Analysis and Evaluation by Insect-Mediated Baiting Reveal Different Patterns of Hypocrealean Entomopathogenic Fungi in the Soils From Two Regions of China

“…In this study, Metarhizium and Beuaveria were relatively abundant across all sampling sites. Prior studies that have laid emphasis on the ability of these generalist fungi to interact with plants, suggesting that the type of vegetation canopy may be associated with their widespread distribution in ecosystems (Wyrebek et al, 2011;Behie et al, 2012;Behie and Bidochka, 2013;Kepler et al, 2015;Keyser et al, 2015;McKinnon et al, 2017McKinnon et al, , 2018Tall and Meyling, 2018). Thus, based on the unique relationship of Metarhizium and Beauveria lineages with the plant rhizospheres, the high frequencies with which these are found in the forest habitats and the grassland habitats can be conceivably illustrated by adding an analysis of fungal-plant associations to the study.…”