Abstract
BackgroundAphids (Hemiptera: Aphididae) are insects with one of the highest potentials for invasion. Several aphid species are present globally due to introduction events; they represent important pests of agroecosystems. The bird cherry-oat aphid Rhopalosiphum padi (Linnaeus) is a major pest of cereals and pasture grasses worldwide. Here, we report the genetic features of populations of R. padi that colonize different cereal crops in central Chile.MethodsRhopalosiphum padi individuals were collected in central Chile and genotyped at six microsatellite loci. The most frequent multilocus genotype (MLG) was then studied further to assess its reproductive performance across cereal hosts under laboratory conditions.ResultsPopulations of R. padi in Chile are characterized by a low clonal diversity (G/N = 62/377 = 0.16) and the overrepresentation of a few widely distributed MLGs. One of the MLGs constituted roughly half of the sample and was observed in all sampled populations at high frequencies. Furthermore, this putative aphid “superclone” exhibited variations in its reproductive performance on cereals most commonly cultivated in Chile. The sampled populations also exhibited weak signs of genetic differentiation among hosts and localities. Our findings suggest that (1) obligate parthenogenesis is the primary reproductive mode of R. padi in Chile in the sampled range and (2) its introduction involved the arrival of a few genotypes that multiplied asexually.
Highlights
Worldwide, roughly 30% of crops are lost due to pests and pathogens
By sampling R. padi individuals from main cereals and genotyping with six microsatellite loci, we showed that these populations are characterized by low genetic diversity, strong indications of the presence of obligate parthenogenetic as a unique reproductive mode, and the dominance of one single genotype with features of a superclone
Genetic features of R. padi in Chile suggest a primary reproductive mode of obligate parthenogenesis We found that Chilean populations of R. padi exhibited low clonal diversity and low genetic diversity compared with sexual populations from elsewhere around the world
Summary
Roughly 30% of crops are lost due to pests and pathogens. Worryingly, these yield losses are expected to increase due to global warming, for major grain crops (e.g., wheat, rice, and maize) in temperate regions (Riegler, 2018). Asexual reproduction of a few genotypes favored the invasion of the cereal aphid Rhopalosiphum padi in Chile. This trend arises because insect pests feed more in warmer climates and rapidly multiply. One of the MLGs constituted roughly half of the sample and was observed in all sampled populations at high frequencies This putative aphid “superclone” exhibited variations in its reproductive performance on cereals most commonly cultivated in Chile. Our findings suggest that (1) obligate parthenogenesis is the primary reproductive mode of R. padi in Chile in the sampled range and (2) its introduction involved the arrival of a few genotypes that multiplied asexually
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