Grain aphid population structure: no effect of fungal infections in a 2‐year field study in Denmark

Abstract

1 Sitobion avenae (F.) is a serious pest in Danish cereal crops. To understand the population genetic structure, aphids were sampled in seven different winter wheat ( Triticum sativum Lamarck) fields throughout Denmark. The aphids were genotyped with seven microsatellite markers. In total, 2075 aphids were collected and 1203 of these were genotyped. 2 The Danish S. avenae populations displayed very high genotypic diversity, high percentages of unique genotypes and low linkage disequilibria; this is likely to be a result of genetic recombination encompassed by their holocyclic lifestyle. The populations showed very limited differentiation and no sign of isolation by distance. Almost all the genetic variation was ascribed within the populations rather than between populations, probably due to a high migration rate at approximate 10% per generation. 3 Seasonal changes in clonal diversity and distribution of asexual summer generations of S. avenae within the infestation period in a single winter wheat field were followed over two consecutive years by weekly sampling from 60 plots each of 20 × 20 m. Clonal diversity was high in all samples with no dominant clonal lineages and no significant difference in the genotypic diversity between weeks or between years. However, a temporal genetic differentiation effect, throughout the infestation, suggests that selective factors or high temporal migration play an important role in shaping the genetic structure S. avenae . 4 Analyses of fungal infected and uninfected aphids were performed to test whether some clonal linage were more often infected by fungi from the Entomophthorales under field conditions. In total, 54 progeny from aphids with Entomophthorales were genotyped and compared with 422 uninfected aphid genotypes. The Entomophthorales-infected aphid genotypes did not cluster out together, suggesting that these fungal pathogens did not affect the population differentiation or clonal distribution of S. avenae in a Danish agroecosystem. 5 Our findings indicate that S. avenae populations can be controlled using conservation biological control

Secretome of fungus-infected aphids documents high pathogen activity and weak host response

“…To ensure enrichment of the library with cDNAs specific to the host-pathogen interaction, we sampled aphids during a natural fungal epidemic. Aphid populations in arable land are typically infected with more than one entomophthoralean species (Jensen et al, 2008). On collection days, E. planchoniana was the most prevalent (15-27% of infected aphids), followed by P. neoaphidis (4-8%), and with only a few percent infected by C. obscurus (Fig.…”

“…1A and B) was followed during one growth season in a Danish organically grown winter wheat field to determine the appropriate time for sampling potentially infected individuals. Species composition was determined by weekly sampling and incubation of 100 live aphids until spore discharge allowed morphological examination, as described in Jensen et al (2008). When fungal infection prevalence increased, thousands of live aphids were brought into the laboratory (Fig.…”

“…Entomophthoralean fungi can cause epidemics in host populations, both in natural habitats and under crop conditions (Hesketh et al, 2010). This has led to the suggestion of using entomophthoralean species as biocontrol agents for pest insects, such as aphids (Hountondji, 2008;Jensen et al, 2008;Nielsen et al, 2005).…”

Differential Performance of <I>Sitobion avenae</I> Populations From Both Sides of the Qinling Mountains Under Common Garden Conditions

“…There are some studies that used molecular markers to examine genetic differentiation of S. avenae populations in China and Europe (Simon et al 1999, Fievet et al 2007, Jensen et al 2008, Xu et al 2011, but variations in the limited loci used may not reßect the extent of changes in their life-history traits. We hypothesize that the separation of Qinling Mountains can cause increasing life-history divergence and local adaptation of S. avenae populations in northern and southern Shaanxi Province, thus creating different population structuring patterns in those areas.…”

The Occurrence of Two Species of Entomophthorales (Entomophthoromycota), Pathogens ofSitobion avenaeandMyzus persicae(Hemiptera: Aphididae), in Tunisia

“…Integrated pest management (IPM) can be seen as a sustainable control strategy to manage pest insects like aphids [6]. Field observations have shown that aphid populations are commonly regulated by a range of natural enemies, such as predators, parasitoids, and also fungal pathogens [7]. In temperate regions, fungal species from the phylum Entomophthoromycota are important pathogens of aphids [8–10].…”