Characterisation of the Viral Community Associated with the Alfalfa Weevil (Hypera postica) and Its Host Plant, Alfalfa (Medicago sativa)

Abstract

Advances in viral metagenomics have paved the way of virus discovery by making the exploration of viruses in any ecosystem possible. Applied to agroecosystems, such an approach opens new possibilities to explore how viruses circulate between insects and plants, which may help to optimise their management. It could also lead to identifying novel entomopathogenic viral resources potentially suitable for biocontrol strategies. We sampled the larvae of a natural population of alfalfa weevils (Hypera postica), a major herbivorous pest feeding on legumes, and its host plant alfalfa (Medicago sativa). Insect and plant samples were collected from a crop field and an adjacent meadow. We characterised the diversity and abundance of viruses associated with weevils and alfalfa, and described nine putative new virus species, including four associated with alfalfa and five with weevils. In addition, we found that trophic accumulation may result in a higher diversity of plant viruses in phytophagous pests compared to host plants.

Diversity of the virome associated with alfalfa (Medicago sativa L.) in the U.S. Pacific Northwest

“…The ORF had best BLAST hits with Watson virus (QED21508.1) and Hypera postica-associated iflavirus 2 (HPAV, QUS52853.1). The former is an unclassified picornavirus reported from Australian fleas 21 and the latter was recently found in larvae of alfalfa weevils ( Hypera postica ), a herbivorous pest feeding on alfalfa and other legumes 22 . As of today, the only known plant-infecting ifla-like virus has been identified from asymptomatic tomato plants 23 .…”

A Novel Flavi-like Virus in Alfalfa (Medicago sativa L.) Crops along the Snake River Valley

“…Two other common viruses found outside of North America are alfalfa enation virus (AEV, genus Nucleorhabdovirus) and lucerne transient streak virus (LTSV, genus Sobemovirus), which are transmitted by aphids and beetles, respectively [2]; the latter has been recently described in the U.S in thrips and alfalfa [3,4]. With the advent of HTS, systematic study of the alfalfa virome became possible and yielded multiple known and new plant viruses identified in different countries over the last several years [3][4][5][6][7][8][9][10][11][12][13][14]. In addition to the common viruses known to infect alfalfa and other crops, a group of persistent viruses was identified in alfalfa, including Medicago sativa alphapartitiviruses 1 and 2 (MsAPV1 and MsAPV2), Medicago sativa deltapartitivirus 1 (MsDPV1), and Medicago sativa amalgavirus 1 (MsAV1) [5,6,[13][14][15][16][17][18].…”

“…In addition to the common viruses known to infect alfalfa and other crops, a group of persistent viruses was identified in alfalfa, including Medicago sativa alphapartitiviruses 1 and 2 (MsAPV1 and MsAPV2), Medicago sativa deltapartitivirus 1 (MsDPV1), and Medicago sativa amalgavirus 1 (MsAV1) [5,6,[13][14][15][16][17][18]. Although several viruses, such as AMV, BLRV, and persistent viruses, are common in alfalfa crops grown around the world, many viruses identified in alfalfa using HTS display a more limited, localized distribution characteristic of a specific country or even a smaller geographic location [5][6][7][8][9][10][11][12][13]. Given the perennial nature of alfalfa stands, these occasional finds of various plant viruses normally associated with other crops seem to suggest a role of alfalfa as a reservoir of pathogens, potentially threatening agricultural production of many crops [4,5].…”

“…Given the perennial nature of alfalfa stands, these occasional finds of various plant viruses normally associated with other crops seem to suggest a role of alfalfa as a reservoir of pathogens, potentially threatening agricultural production of many crops [4,5]. Additionally, because most alfalfa-infecting viruses have insect vectors, HTS was also applied for virome studies of insect pests found in alfalfa fields, such as thrips, aphids [18], and weevils [8], and in addition to plant viruses ingested by the insects [18], multiple sequences from arthropod viruses were detected [8]. The majority of the reads assigned to arthropod viruses in alfalfa weevils belong to the families Iflaviridae and Solemoviridae [8].…”

Virome Analysis Reveals Diverse and Divergent RNA Viruses in Wild Insect Pollinators in Beijing, China

“…For example, while the Lake Sinai virus (LSV) has been classified as Nodamuvirales, the LSV-containing clade has been shown to be distinct from the Nodaviridae family in an unrooted phylogenetic tree [26,27]. Interestingly, although Hypera postica-associated sinaivirus in the Sinhaliviridae family has been detected in Hypera postica, this virus is most closely related to the LSV [28]. Therefore, a study of viruses in host-related species has the potential to clarify as-yetundefined viral evolutionary relationships.…”