Systemic acropedal influence of endophyte seed treatment on Acyrthosiphon pisum and Aphis fabae offspring development and reproductive fitness

Most terrestrial plants harbor endophytic fungi, and many of them could directly or indirectly influence insect behavior and community structures by altering plant defense mechanisms. Therefore we evaluated the systemic effects of endophyte seed treatment on aphid population growth rate, offspring performance and fecundity and its effects on Vicia faba in response to aphid feeding. Overall, endophyte treated fava beans had a significantly lower number of Acyrthosiphon pisum when compared to the untreated controls. The highest reduction effects were observed among plants treated with Trichoderma asperellum, Gibberella moniliformis and Beauveria bassiana isolates, while all Metarhizium anisioplaie and Hypocrea lixi isolates had the least effects on A. pisum population growth. Similarly, endophyte seed treatment had a detrimental effect on offspring fitness, development and fecundity. Irrespective of aphid species, the birth rate of all offspring arising from females fed on endophyte treated plants for two generations were significantly lower than those arising from females fed on control plants. As a result, all endophyte treated plants had between 1.6–14.6 and 3.7–11.0 times less number of Aphis fabae and A. pisum nymphs, respectively, compared to untreated controls at the final assessment day. Concurrently, endophyte seed treatment enhanced seedling survivorship with a survival rate of 20–100% compared to none in the control treatment at 20 days post infestation. The present study demonstrates that endophyte seed treatment can offer a protective role by enhancing the competitiveness of V. faba towards aphids, which can be manipulated as a tool in IPM systems.

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► Fava bean seeds soaked in endophyte spore suspension for 4 h in tween/water solution.
► Seedlings grown in the greenhouse for 21 days and then root ball re-inoculated with the endophyte.
► Aphid development and fecundity was monitored following aphid infestation.
► Endophyte seed treatment slowed offspring development and reduced fecundity rate by a factor of 1.6–14.6.