Monitoring of the Apple Fruit Moth: Detection of Genetic Variation and Structure Applying a Novel Multiplex Set of 19 STR Markers

Abstract

The apple fruit moth Argyresthia conjugella (Lepidoptera, Yponomeutidae) is a seed predator of rowan (Sorbus aucuparia) and is distributed in Europe and Asia. In Fennoscandia (Finland, Norway and Sweden), rowan fruit production is low every 2–4 years, and apple (Malus domestica) functions as an alternative host, resulting in economic loss in apple crops in inter-mast years. We have used Illumina MiSeq sequencing to identify a set of 19 novel tetra-nucleotide short tandem repeats (STRs) in Argyresthia conjugella. Such motifs are recommended for genetic monitoring, which may help to determine the eco-evolutionary processes acting on this pest insect. The 19 STRs were optimized and amplified into five multiplex PCR reactions. We tested individuals collected from Norway and Sweden (n = 64), and detected very high genetic variation (average 13.6 alleles, He = 0.75) compared to most other Lepidoptera species studied so far. Spatial genetic differentiation was low and gene flow was high in the test populations, although two non-spatial clusters could be detected. We conclude that this set of genetic markers may be a useful resource for population genetic monitoring of this economical important insect species.

Large-scale genetic admixture suggests high dispersal in an insect pest, the apple fruit moth

“…The more than ten times larger dataset and the high number of alleles in the present study may additionally reduce this loss in power to detect genetic structure. Thus, we conclude that the alternative use of all 19 STRs [41] may not represent a cost-benefit for the analysis and would only lead to a minimal increase in the sensitivity of the genetic structure analysis. The lower cost and time-saving strategy in our study included selecting the 10 STRs with the best performance and highest genetic variation.…”

“…From our previous work on apple fruit moths [41], we selected 10 out of 19 tetranucleotide STRs for the present study. We based our selection of STRs on a combination of high number of alleles, optimal peak height, and clear interpretation (results not shown).…”

“…Based on these results, we concluded that genotyping and scoring errors or other lab-related errors can be excluded as potential causes for obtained genetic patterns in this study. Finally, we also tested the difference in power to detect genetic differentiation and structure with the smaller dataset (n = 64) from the previous study [41], applying two STRUCTURE runs with the 10 selected STRs as well as the total set of 19 STR markers. This test indicated only a minor loss of power for the 10 STRs relative to whole set of 19 STRs (results not shown).…”

“…However, for other Lepidoptera species, genetic similarity and high gene flow have been detected both across distant geographical areas and between different years [2,39]. Recently, we have shown that the apple fruit moth may have high genetic variation and local genetic structure [40,41]. As an extension of these earlier studies, our aim was to investigate if the apple fruit moth expresses any broader genetic structures, or if gene flow may be high across the four very different climatic zones (from temperate to polar) on the Scandinavian Peninsula.…”

“…To achieve this goal, we collected 669 individuals of the apple fruit moth over an area of approx. 850,000 km 2 and subjected all individuals to genetic analysis with validated short tandem repeats (STR) genetic markers [41].…”