Local Aphid Species Infestation on Invasive Weeds Affects Virus Infection of Nearest Crops Under Different Management Systems - A Preliminary Study.

Attila-Károly Szabó,József Kiss,Adalbert Balog,Hugh D Loxdale,Zsuzsanna Nagyné Galbács,Emese Demian,Éva Várallyay,Anna Hegyi,János Bálint

doi:10.3389/fpls.2020.00684

Abstract

In the present study, we conducted field surveys to detect the population density of the most important invasive weed species and their associated virus vectoring aphids in crops grown under high input field (HIF) vs. low-input field (LIF) conditions, with and without fertilizers and pesticides. The most frequent invasive weed species were annual fleabane, Erigeron annua (L.), Canadian horseweed, Erigeron canadensis (L.) and Canadian goldenrod, Solidago canadensis (L.). These species were predominantly hosts of the aphids Brachycaudus helichrysi and Aulacorthum solani under both management systems. The 13% higher coverage of E. annua under LIF conditions resulted in a 30% higher B. helichrysi abundance and ∼85% higher A. solani abundance compared with HIF conditions. To reveal the incidence of virus infection in crop plants and invasive weeds, high-throughput sequencing of small RNAs was performed. Bioinformatics analysis combined with independent validation methods revealed the presence of six viruses, but with strikingly different patterns under LIF and HIF conditions. Their presence without symptoms in invasive weeds and crop plants supports the necessity of employing new approaches to those currently employed in invasive weed management. These findings also suggest that invasive weeds could serve as hosts for local aphid species and reservoirs for plant pathogenic viruses, both under low and high input management systems. In this light, as here demonstrated, viruses transmitted by local aphid species were found to differ between the management systems; hence, the importance of B. helichrysi and A. solani as virus vectors in particular clearly needs to be re-evaluated. Altogether, we accept that the present study is a pilot one and individual virus vectoring of aphids still needs to be directly tested. Even so, it represents one of the first contributions to this particular area, and thereby paves the way for further similar applied research in the future.

Highlights

MATERIALS AND METHODSInvasive weeds represent a serious threat to world crop production as global trade expands and climatic conditions shift (Agrow, 2015; Usda Forest Service, 2015)
As the crops investigated belonged to different families, and as such hosted very different viruses, we investigated their viral patterning as a collective pool
S. canadensis was only present in low-input field (LIF), with a coverage of 2.5%

Summary

Introduction

Invasive weeds represent a serious threat to world crop production as global trade expands and climatic conditions shift (Agrow, 2015; Usda Forest Service, 2015). In this light, it has recently been suggested that the losses to crop yield caused by invasive weeds and their infesting aphids (Hemiptera: Aphididae), may increase substantially (by around 25%) within the EU over the few years (Usda Forest Service, 2015; EPPO, 2017). Weed control strategies involve apparently useful approaches, including physical (e.g. mulching, tilling, burning) and chemical and other control (e.g. use of high quality seeds, crop rotation, herbicide application) (Chitsaz and Nelson, 1983; Rand and Louda, 2004; Uchino et al, 2012; Mabuza et al, 2013), the net areas covered by invasive weed species continues to increase in Central European regions (Tunaitieneet al., 2015; Pacanoski, 2017)

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