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Title: Root environment is a key determinant of fungal entomopathogen endophytism following seed treatment in the common bean, Phaseolus vulgaris

Author
item PARA, SOROUSH - International Center For Tropical Agriculture (CIAT)
item ORTIZ, VIVIANA - International Center For Tropical Agriculture (CIAT)
item GOMEZ-JIMENEZ, MARIA - International Center For Tropical Agriculture (CIAT)
item Kramer, Matthew
item Vega, Fernando

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2016
Publication Date: 12/1/2017
Citation: Para, S., Ortiz, V., Gomez-Jimenez, M.I., Kramer, M.H., Vega, F.E. 2017. Root environment is a key determinant of fungal entomopathogen endophytism following seed treatment in the common bean, Phaseolus vulgaris. Biological Control. 116:74-81.

Interpretive Summary: The common bean (Phaseolus vulgaris) can be affected by more than 400 insect pests and 200 plant pathogens, whose attack is thought to be the most limiting bean production factor across many regions. Accordingly, the common bean may be an excellent candidate crop to examine the full spectrum of endophytic biological control by the fungal insect pathogens Beauveria bassiana and Metarhizium anisopliae. This article describes seed soaking as an effective method in introducing both insect pathogens as endophytes in the common bean and reveals the high variability in results due to the use of non-sterile soils. This information will be of use to mycologists, entomologists, microbiologists, and practitioners of biological control of insect pests.

Technical Abstract: The common bean is the most important food legume in the world. We examined the potential of the fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae applied as seed treatments for their endophytic establishment in the common bean. Endophytic colonization in sterile sand:peat averaged ca. 40% higher for treatment fungi and ca. six times higher for volunteer fungi (other fungal endophytes naturally occurring in our samples), relative to sterile vermiculite. Colonization by treatment endophytes was least variable in sterile vermiculite and most variable in sterile soil:sand:peat. A separate experiment assessed the impact of soil sterilization on endophytic colonization using six different field-collected soils. Soil sterilization was the variable with the largest impact on colonization (70.8% of its total variance), while the fungal isolate used to inoculate seeds explained 8.4% of the variance. Under natural microbial soil conditions experienced by farmers, seed inoculations with fungal entomopathogens are unlikely to yield predictable levels of endophytic colonization.