Ali, Jamin (2022) The chemical ecology of a model aphid pest, Myzus persicae, and its natural enemies. Doctoral thesis, Keele University.

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The peach potato aphid, Myzus persicae, is a serious crop pest with a worldwide distribution. It has short generation time, high reproductive rate and the ability to adapt to new hosts and develop resistance against major class of insecticides. There is an urgent need to develop eco-friendly and sustainable new ways to protect plants from this cosmopolitan pest.

The aim of this project was to study the chemical ecology of multitrophic interactions of M. persicae with its host plants and natural enemy, Diaeretiella rapae. Potato (wild Solanum stoloniferum vs. cultivated Solanum tuberosum Desiree) and brassica (Brassica napus, Brassica rapae) plants were used to study the behavioural responses and performance of insects. To explore plant defence induction, the effect of a plant defence elicitor, cis-Jasmone, was also tested on brassica plants. For this, we performed a series of insect performance and behavioral bioassays and headspace sampling of plants for volatile collection. In this project, M. persicae showed a negative response towards the wild potato plants in performance and behavioral bioassay. The wild accessions had a high reduction in aphid survival and larviposition after both time points 48 h and 96 h. A significant change in volatile emission was also recorded when volatile analysis was performed for wild and cultivated potatoes. The volatile compounds released by wild potato were highly repellent to aphid M. persicae but acted as an attractant to parasitoid D. rapae. Conclusively, wild potato showed a high potential of reducing M. persicae population by direct (high mortality and low larviposition) and indirect defenses (enhanced parasitoid foraging time).

We also tested the effect of CJ treatment on brassica crops, the obtained results showed that CJ treated brassica lines were highly resistant to M. persicae throughout the series of experiments. The performance of M. persicae was significantly reduced on CJ treated brassica lines in clip-cage and settlement bioassay. The volatile compounds collected from CJ treated brassica lines also had repellent effect on M. persicae. In contrast, CJ treatment had a positive effect on D. rapae and a positive behavioral response of D. rapae was recorded towards CJ treated plants and volatile compounds. A significant increase in parasitoid foraging time and parasitism behavior was recorded on all CJ treated brassica lines. In Olfactometer bioassay, M. persicae spent significant less time when exposed to CJ plant volatile samples while D. rapae spent significant longer time in the olfactometer arm treated with volatile sample collected from CJ treated brassica lines. Volatile analysis also revealed that there was a significant increase in quality and quantity of volatile compounds after brassicas treatment with CJ. Taking altogether, our results showed that CJ treatment induced defence in brassica crops against M. persicae by affecting pest performance and increasing biological control. These results could contribute towards developing novel management approaches for the pest.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QH Natural history
Divisions: Faculty of Natural Sciences > School of Life Sciences
Contributors: Bruce, TJA (Thesis advisor)
Depositing User: Lisa Bailey
Date Deposited: 14 Oct 2022 15:52
Last Modified: 14 Oct 2022 15:52

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