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Published on: April 23, 2012
Observations on the Relationships between Endophytic Metarhizium robertsii, Spodoptera frugiperda (Lepidoptera:
Brianna Flonc1,2, Mary Barbercheck1, Imtiaz Ahmad1
1Department of Entomology, The Pennsylvania State University, University Park, PA 16802, USA.
Abstract:
Fungi in the genus Metarhizium are entomopathogens that can establish endophytically inside plants and benefit them through growth promotion and pest suppression. Lab- and greenhouse-based experiments were conducted to examine the effects of endophytic M. robertsii colonization in maize (Zea mays) on fall armyworm (FAW) (Spodoptera frugiperda). Maize seeds were inoculated with M. robertsii conidia, plants were evaluated for endophytic colonization, and then relative growth rate (RGR) and feeding behavior of larval FAW fed leaves from inoculated and uninoculated maize were measured. Endophytic M. robertsii was recovered from 60.5% of inoculated maize. In feeding bioassays, the RGR of larval FAW fed leaves of inoculated maize was no different than the RGR of larvae fed leaves from uninoculated maize. The RGR of larval FAW was positively correlated with the proportion of endophytic colonization of maize leaf and root tissues; however, in feeding assays, FAW larvae demonstrated no preference for consuming leaf tissue from inoculated or uninoculated maize. The proportion of leaf tissue consumed was unrelated to the proportion of M. robertsii-colonization of leaf or root tissue from source plants. We discuss possible reasons why FAW were not affected by endophytic M. robertsii in the context of assay methodology, FAW physiology, and induced maize defenses.
Insights
Endophytic Metarhizium robertsii colonization in maize did not affect fall armyworm (FAW) growth or feeding behavior. FAW growth correlated with fungal colonization, but larvae showed no preference for or against feeding on colonized maize leaves.
Area of Science:
- Agricultural Science
- Entomology
- Plant Pathology
Background:
- * Entomopathogenic fungi, such as Metarhizium, can colonize plants endophytically.
- * Endophytic fungi may offer benefits to plants, including enhanced growth and pest resistance.
- * The fall armyworm (Spodoptera frugiperda) is a significant agricultural pest.
Purpose of the Study:
- * To investigate the impact of endophytic Metarhizium robertsii colonization in maize (Zea mays) on the fall armyworm (FAW).
- * To assess how endophytic colonization affects FAW larval growth rate and feeding behavior.
Main Methods:
- * Maize seeds were inoculated with M. robertsii conidia.
- * Endophytic colonization of maize tissues was confirmed.
- * Larval FAW were fed leaves from inoculated and uninoculated maize in feeding bioassays.
- * Relative growth rate (RGR) and leaf consumption were measured.
Main Results:
- * Endophytic M. robertsii was successfully recovered from 60.5% of inoculated maize plants.
- * No significant difference in FAW larval RGR was observed between larvae fed leaves from inoculated versus uninoculated maize.
- * FAW larval RGR was positively correlated with the proportion of endophytic colonization in maize leaves and roots.
- * FAW larvae did not show a feeding preference for leaves from inoculated or uninoculated maize.
- * Leaf tissue consumption was not related to the level of M. robertsii colonization.
Conclusions:
- * Endophytic M. robertsii colonization in maize did not confer direct protection against FAW in this study.
- * The lack of effect may be due to assay methodology, FAW physiology, or induced plant defenses.
- * Further research is needed to understand the plant-fungus-insect interactions.
