Response of the melon aphid, Aphis gossypii, to host‐plant resistance: evidence for high adaptive potential despite low genetic variability

Abstract

In agrosystems, pests are submitted to strong human‐imposed selective pressures to which they sometimes adapt rapidly, either through selection of genotypes resulting from mutation and/or recombination events, or through phenotypic plasticity. Understanding how insects respond to such selective pressures is of great importance for sustainable pest management strategies, such as the use of resistant plants. In this study, we investigated the genetic and phenotypic variability of anholocyclic Aphis gossypii Glover (Hemiptera: Aphididae) strains, in response to the resistance gene Vat that is present in melon crops. Forty‐nine aphid colonies were sampled on several melon crops in southern France, genotyped using 15 microsatellite loci, and tested in phenotypic experiments using Vat or non‐Vat melons. The level of genetic polymorphism between these colonies was low, as only seven multilocus genotypes were detected. In contrast, the phenotypic variability for life‐history and behavioral traits between colonies, including those sharing the same genotype, was unexpectedly high, with a continuum of response to the Vat gene from complete susceptibility to strong virulence. The low genetic polymorphism associated with a strong phenotypic variability highlights the high adaptive potential of A. gossypii and the major role of environmental cues in shaping phenotypic responses of this aphid to pest management strategies.

Insight into the durability of plant resistance to aphids from a demo‐genetic study of Aphis gossypii in melon crops

“…These findings are consistent with those of a previous laboratory study (Lombaert et al. ) showing that Vat ‐mediated resistance affects the biotic potential of 90% of cluster III clones (NM1) and only 40% of clones assigned to cluster I or II on the basis of their MLG. This selective process has been at work for years in the SE, following the widespread deployment of Vat varieties over the agricultural landscape over the last 15 years, as NM1 accounted for 30% of the spring migrant population in 2004 but has not been observed since 2013.…”

Resistance induction and herbivore virulence in the interaction between Myzus persicae (Sulzer) and a major aphid resistance gene (Rm2) from peach

“…In melon, Vat confers both resistance to the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), and resistance to nonpersistent viruses when transmitted by this same aphid species. Lombaert et al (2009) detected in aphid populations a continuum of performance response to Vat from complete avirulence to strong virulence, but no variability and no overcoming of Vat resistance were observed for the trait ''virus transmission''. This suggests that A. gossypii is effectively recognized by Vat melon plants, even if the trait ''plant resistance'' is overcome.…”

“…Today, predicting the evolution of resistance conferred by Rm2 is difficult. On the one hand, a previous microsatellite analysis exposed a large spatial and temporal genetic variability in French populations of M. persicae (Guillemaud et al 2003a), theoretically necessary to allow adaptive genes to evolve (but see Lombaert et al 2009). In addition, M. persicae contains considerable genetic variation for host plant adaptation (Weber 1985;Nikolakakis et al 2003), and insecticide resistance has evolved in the populations from which aphids used in the present work were sampled (Guillemaud et al 2003b).…”

Rearing history affects behaviour and performance of two virulent Nasonovia ribisnigri populations on two lettuce cultivars

“…More nymphs were produced on the susceptible wheat and resistant oats by aphids that were reared on susceptible wheat than by aphids reared on resistant oats. Although no effects of plant of origin were found for Aphis gossypii (Glover) colonies collected from the field and tested on resistant and susceptible melon cultivars, an effect of laboratory rearing on cucumber was found: the longer the colony was reared on cucumber, the higher aphid fecundity was on resistant melon (mediated by the Vat ‐gene) and the poorer on susceptible melon (Lombaert et al., ).…”