Host‐adapted aphid populations differ in their migratory patterns and capacity to colonize crops

Abstract

1. Although phytophagous insects can vary genetically in host use and exhibit long-range movements, the combined implications of these phenomena for pest management have received limited attention. 2. To address this, we surveyed the genetic diversity of pea aphid Acyrthosiphon pisum using twelve microsatellite loci and assessed host association patterns and annual movement from a putative source region (Columbia River Basin) to the Palouse region of northern Idaho and western Washington, where the aphid is a pest of pea Pisum sativum. 3. A total of 320 identified unique genotypes clustered into four genetic groups, with two host plant associations: alfalfa Medicago sativa (three genetic groups), and pea Pisum sativum and vetch Vicia villosa (one genetic group). All four genetic groups occurred in the Columbia River Basin and in migrant aphids collected in pan traps during spring colonization in the Palouse during 2 years of this study. Patterns of group arrival on the Palouse were spatially structured early in the season, consistent with differing migration patterns. Despite genetic diversity of migrants, a single genetic group became predominant in pea crops each year. 4. Clonal laboratory colonies of pea aphids established from field-collected specimens and representing two predominant genetic groups exhibited reciprocal performance trade-offs, with alfalfa being a poor host for a pea-associated aphid genotype and vice versa. 5. Synthesis and applications. Annual spring migrants of pea aphids in the pea production region of the Palouse are genetically diverse, with different host plant affinities consistent with origination from source populations in the Columbia River Basin. As the season progresses, a single genetic group adapted to pea becomes predominant in the crop. Management of pea aphid in the Palouse will be improved by monitoring the temporal and spatial variation of specific genetic groups of the aphid arriving as immigrants during each crop season, providing this information to producers and adjusting estimates of risk of crop damage accordingly. The principle could apply to other pest species with host-adapted populations that colonize crops on an annual basis.

Using NextRAD sequencing to infer movement of herbivores among host plants

“…For example, outbreaks of bean leaf roll viruses damaging to leguminous crops often depend upon movement of pea aphid ( Acyrthosiphon pisum ) vectors from alfalfa ( Medicago sativa L.), a perennial host of both aphid and virus, onto peas [66]. This general movement of aphid between these two host plants has been documented using microsatellite markers in the pea aphid (e.g., [67]). However, sequencing approaches that detail SNPs across the genome, such as the NextRAD, could reveal fine-scaled population structure and thus infer aphid and virus movement among particular fields within a growing region (e.g., Figs 2 and 3).…”

Risk assessment for non‐crop hosts of pea enation mosaic virus and the aphid vector Acyrthosiphon pisum

“…Our understanding of pea aphid and PEMV outbreaks in the Palouse considers that pea aphids likely colonize Palouse agroecosystems following wind currents from the Columbia Basin and Willamette Valley, where milder winters allow aphids to overwinter on alfalfa and clover (Clement et al, 2010; Hampton, 1983). Genetic data show that the pea aphid biotype found on dry pea in the Palouse has shared markers with biotypes collected in these areas (Eigenbrode et al, 2016). Our study suggests two possibilities that align with this information.…”

Using host‐associated differentiation to track source population and dispersal distance among insect vectors of plant pathogens

“…The total A. craccivora trapped per field was comparable to that of a previous study in area pumpkin fields Year 2 (2013) 28 25 3 13 8 5 (Angelella et al, 2015), and to that of a similar study of Ac. pisum migrant population genetics in peas (Eigenbrode et al, 2016). However, because migrant trap catches can be quite low within crop fields, it is possible that patterns in MLG composition could be impacted by sample size and the ability to obtain a representative sample.…”

“…Importantly, aphids exhibit a suite of life history characteristics (e.g., asexual reproduction) that make them prone to exhibit HAD (Dickey & Medina, 2010), and many populations display some sort of underlying genetic structure according to hostplant or geography (Delmotte, Leterme, Gauthier, Rispe, & Simon, 2002;Guillemaud, Mieuzet, & Simon, 2003;Loxdale & Lushai, 2007;Loxdale et al, 2011;Orantes, Wei Zhang, Mian, & Michel, 2012;Wilson, Sunnucks, Blackman, & Hales, 2002). However, few studies have used HAD-mediated population differences to infer the source and movement of key plant pathogen vectors: one recent study used microsatellite loci to identify the originating host plants for pea aphids, Acyrthosiphon pisum, migrating into legume crops across the north-western United States (Eigenbrode et al, 2016).…”