Asexual reproduction is very common in invasive insect pest. In the recent years, increasing evidences have shown that some invasive asexual lineages display an outstanding capacity to predominate in space and persist on time (superclones). However, little is known about the host-use behavior of these superclones. The English grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae) is one of the major pests of cereals worldwide. Chilean populations of the grain aphid are characterized by a high degree of heterozygosity and low genotypic variability across regions and years, with only four predominant superclone genotypes representing nearly 90% of populations. In this study, (1) the reproductive performance and (2) the probing behavior followed a host shift of one superclone and one non-superclone of S. avenae, were compared. The host plant in the superclone did not affect the reproductive performance, while in the non-superclone was lower on highly defended wheat seedling. The experimental switching of the host plants from barley (without chemical defenses) to two wheat species with low and high levels of chemical defenses, revealed that superclone exhibited a flexible probing activities related to access of sieve elements, while the non-superclone exhibited rigid responses. These findings are consistent with the pattern of occurrence of these genotypes in the field on cereals with different plant defenses (e.g. benzoxazinoids). These responses are discussed on the view of developing new strategies for the management in invasive populations of aphid pest species.

Background Aphids (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. Methods Rhopalosiphum 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. Results Populations 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.

Abstract. Benzoxazinoids are key defence chemicals in cereals that are known to affect several aspects of aphid biology. However, little is known about how they affect aphid physiology. In the present study, we report changes in the whole-body proteomic profiles of a 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA)-susceptible genotype of the grain aphid Sitobion avenae (F.) after being exposed to wheat cultivars containing contrasting levels of DIMBOA. The proteome is analyzed after 14 days (short term) and 28 days (long term) of rearing on these cultivars. Seventy-two proteins are differentially regulated among the treatments and 49 are identified. Exposure to high-DIMBOA plants results in a higher number of proteins regulated long term. DIMBOA exposure in S. avenae initially generates greater cellular activities, mostly involving cytoskeleton function and possibly related to detoxification. This function appears to be unimportant at long term and is eventually replaced by effects on metabolism function and homeostasis. Taken together, the results of the present study show that the responses of aphids to the secondary plant compounds, such as DIMBOA, exhibit a temporal dynamic in the proteome, possibly helping aphids to overcome the effect of these toxic compounds.