Effects of cis-Jasmone Treatment of Brassicas on Interactions With Myzus persicae Aphids and Their Parasitoid Diaeretiella rapae.

Jamin Ali,William D J Kirk,Toby J A Bruce,Anca D Covaci,Islam S Sobhy,Joe M Roberts

doi:10.3389/fpls.2021.711896

Jamin Ali, William D J Kirk + Show 4 more

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https://doi.org/10.3389/fpls.2021.711896

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Abstract

There is a need to develop new ways of protecting plants against aphid attack. Here, we investigated the effect of a plant defence activator, cis-jasmone (CJ), in a range of cultivars of Brassica napus, Brassica rapa and Brassica oleracea. Plants were sprayed with cis-jasmone or blank formulation and then tested with peach potato aphids (Myzus persicae Sulzer) (Hemiptera: Aphididae) and their parasitoid Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae). CJ treated plants had significantly lower aphid settlement than control plants in a settlement bioassay. Conversely, in a foraging bioassay, D. rapae parasitoids spent a significantly longer time foraging on CJ treated plants. Our results reveal that CJ treatment makes plants less attractive to and less suitable for M. persicae but more attractive to D. rapae in a range of brassica cultivars. It is likely that these effects are due to changes in volatile emission indicating activation of defence and presence of conspecific competitors to aphids but presence of prey to parasitoids. Increases in volatile emission were found in CJ induced plants but varied with genotype. Among the synthetic volatile compounds that were induced in the headspace of CJ treated brassica cultivars, methyl isothiocyanate, methyl salicylate and cis-jasmone were most repellent to aphids. These results build on earlier studies in Arabidopsis and show that tritrophic interactions are influenced by CJ in a wide range of brassica germplasm. The implication is that CJ is a promising treatment that could be used in brassica crops as part of an integrated pest management system.

Highlights

Cis-Jasmone (CJ) is a benign plant defence activator shown to have considerable promise in enhancing plant defence against hemipteran insect pests in Arabidopsis thaliana (Bruce et al, 2008) as well as crops such as wheat (Bruce et al, 2003a,b), maize (Oluwafemi et al, 2013), cotton (Hegde et al, 2012), sweet pepper (Dewhirst et al, 2012) and potato (Sobhy et al, 2017, 2020)
Our study focused on Myzus persicae Sulzer (Hemiptera: Aphididae), commonly known as peach potato aphid, because it is the main aphid pest of brassica crops
After 48 h there was no significant reduction in adult M. persicae survival on five brassica cultivars treated with CJ in clip cage experiments (Figure 1A)

Summary

Introduction

Cis-Jasmone (CJ) is a benign plant defence activator shown to have considerable promise in enhancing plant defence against hemipteran insect pests in Arabidopsis thaliana (Bruce et al, 2008) as well as crops such as wheat (Bruce et al, 2003a,b), maize (Oluwafemi et al, 2013), cotton (Hegde et al, 2012), sweet pepper (Dewhirst et al, 2012) and potato (Sobhy et al, 2017, 2020). It was hypothesised to have a role in plant defence due to structural similarities with the plant hormone jasmonic acid and experimental cis-Jasmone Treatment of Brassicas evidence confirmed this hypothesis. The current study was designed to test the hypotheses that CJ treatment could (1) reduce aphid performance and colonisation and (2) increase parasitoid foraging in a range of cultivars of Brassica napus, B. rapa and B. oleracea. Our study is timely because there is an urgent need for new approaches to crop protection in brassicas as Myzus persicae aphids have evolved resistance to many insecticides (Bass et al, 2014) and the neonicotinoid restriction in Europe has further reduced conventional control options (Dewar, 2017)

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