Spectral sensitivity of L2 biotype in the Thrips tabaci cryptic species complex

Ádám Egri,Péter Farkas,Balázs Bernáth,Patrick M Guerin,József Fail

doi:10.1016/j.jinsphys.2019.103999

Abstract

The onion thrips, Thrips tabaci (Lindeman, 1889), is a cosmopolitan pest of economic importance on a wide range of crops. Despite being one of the most studied thrips species, there is very limited knowledge available about its ability to perceive light. The T. tabaci cryptic species complex consists of a tobacco-associated (T) and two leek-associated (L1, L2) biotypes. We made electroretinogram recordings on the most widespread thelytokous (where unfertilized eggs produce females) T. tabaci L2 biotype and measured attraction to light sources in this biotype as a function of wavelength in behavioural experiments. The spectral sensitivity of the T. tabaci L2 biotype shows a unimodal curve peaking at λmax = 521 nm. Contrary to this spectral sensitivity curve, L2 biotype attraction in an arena is bimodal with local maxima at 368 nm (UV) and 506–520 nm (green) being practically of the same magnitude. Although being similar to the arrhenotokous (where unfertilized eggs produce males) L1 biotype in phototaxis, significant differences regarding photoreceptor cell responses emerged. This study contributes to our understanding of light perception in Thysanoptera as well as to the development of more effective monitoring tools for this economically important pest species.

Highlights

Onion thrips, Thrips tabaci (Lindeman, 1889) (Thysanoptera: Thripidae) is a widely distributed pest of economic importance (Fail, 2016)
The spectral sensitivity curve was determined within the visible spectrum and while only a single wavelength (365 nm) was measured in the UV-A range it became clear that the compound eye of F. occidentalis is maximally sensitive to green and UV light
The strongest attraction of T. tabaci biotype L2 to light was elicited by UV-A (368 nm) and green (506 nm–520 nm) spectral regions (Fig. 8A)

Summary

Introduction

Thrips tabaci (Lindeman, 1889) (Thysanoptera: Thripidae) is a widely distributed pest of economic importance (Fail, 2016). T. tabaci is a vector of two economically significant viral pathogens, Iris yellow spot virus and Tomato spotted wilt virus. The former pathogen is estimated to cause annual losses of U.S $90 million to onion production in the USA alone (Gent et al, 2006) while the latter can cause over U.S $1 billion in crop losses annually worldwide (Goldbach and Peters, 1994). Onion thrips is considered as a cryptic species complex containing these 3 distinct biotypes (Toda and Murai, 2007; Kobayashi and Hasegawa, 2012; Kobayashi et al, 2013; Westmore et al, 2013; Fekrat et al, 2014; Sojnóczki et al, 2015; Jacobson et al, 2016). In arrhenotokous biotypes, unfertilized eggs develop to males, while in thelytokous L2 biotype unfertilized eggs develop into female offspring (Toda and Murai, 2007)

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Results

Conclusion