Genetic Divergence of Two Sitobion avenae Biotypes on Barley and Wheat in China

Abstract

Host plant affinity and geographic distance can play critical roles in the genetic divergence of insect herbivores and evolution of insect biotypes, but their relative importance in the divergence of insect populations is still poorly understood. We used microsatellite markers to test the effects of host plant species and geographic distance on divergence of two biotypes of the English grain aphid, Sitobion avenae (Fabricius). We found that clones of S. avenae from western provinces (i.e., Xinjiang, Gansu, Qinghai and Shaanxi) had significantly higher genetic diversity than those from eastern provinces (i.e., Anhui, Henan, Hubei, Zhejiang and Jiangsu), suggesting their differentiation between both areas. Based on genetic diversity and distance estimates, biotype 1 clones of eastern provinces showed high genetic divergence from those of western provinces in many cases. Western clones of S. avenae also showed higher genetic divergence among themselves than eastern clones. The Mantel test identified a significant isolation-by-distance (IBD) effect among different geographic populations of S. avenae, providing additional evidence for a critical role of geography in the genetic structure of both S. avenae biotypes. Genetic differentiation (i.e., F ST ) between the two biotypes was low in all provinces except Shaanxi. Surprisingly, in our analyses of molecular variance, non-significant genetic differentiation between both biotypes or between barley and wheat clones of S. avenae was identified, showing little contribution of host-plant associated differentiation to the divergence of both biotypes in this aphid. Thus, it is highly likely that the divergence of the two S. avenae biotypes involved more geographic isolation and selection of some form than host plant affinity. Our study can provide insights into understanding of genetic structure of insect populations and the divergence of insect biotypes.

The Peculiarities of Metopolophium dirhodum (Walk.) Population Formation Depending on Its Clonal and Morphotypic Organization during the Summer Period

“…Clones that possess a set of adaptations optimized for all morphotypes will be more successful and will have a greater impact on structuring a pest population and driving its dynamics [ 53 ], but this phenomenon is not yet understood well enough to create models that reliably predict the population dynamics of aphids in agricultural ecosystems [ 26 ]. Because many studies only utilize laboratory populations without accounting for the natural variations in temperature, humidity, and illumination, there is a need to conduct experiments that better simulate natural conditions for a better characterization of the influence that genotype-phenotype relationships have in the life cycles of aphids [ 3 , 21 , 38 , 40 , 54 , 55 ]. The present study addresses this knowledge gap by investigating the features of the clonal composition and development of M. dirhodum morphotypes under semi-natural conditions in Northeastern Europe/Northwestern Russia.…”

“…Polymorphism (polyphenism) allows for the production of alate morphotypes that migrate to herbaceous plants in spring (emigrants), disperse between secondary hosts in summer (alate summer exules; the term “exule” refers to an aphid in the parthenogenetic generation on its secondary host), and bring the sexes together in autumn (males and gynoparae, reproducing oviparae) [ 4 , 32 , 33 , 34 , 35 ]. Genetic methods can be used to study the complexity of the aphid population structure, which provides information not only on the molecular genetic basis on the importance of aphid diversification, but also on the phenotypic diversity in the ontogeny of individual morphotypes and their relative frequencies in different clonal populations [ 4 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

SRAP analysis of brown planthopper (Nilaparvata lugens) populations maintained on differential rice host varieties

“…The highest genetic differentiation (PhiPT 0.133) was observed between population T and R, and the lowest (PhiPT 0.057) was between population T and M (Table 4). These values indicate moderate differentiation among the population based on the threshold of 0.05<PhiPT≤0.15 (Wang et al 2020). However, between all pairs of populations, there was significant genetic differentiation (P=0.01) (Table 4).…”

“…Therefore, phenotypic plasticity shown by BPH population indicates the change in allele frequencies of genes associated with host adaptation. In several insects, including BPH, DNA marker analysis has been employed to study the divergence of biotypes species to understand the basis, i.e., geographic or host plant-associated differentiation (Wang et al 2020). However, the first genetic study using random amplified polymorphic DNA (RAPD) markers in BPH did not indicate genetic divergences among BPH biotypes (Shufran and Whalon 1995).…”

“…In addition, SRAP was reported to be more potent than RAPD analysis for detecting the genetic polymorphism among closely related species (ElAzim et al 2019). SRAP markers have gained popularity in studies of genetic diversity, genetic linkage map construction and comparative genetics in various crops (Li et al 2014;Robarts and Wolfe 2014) and to a lesser extent in studies of genetic diversity of plantpathogen (Tripathi and Dubey 2015;Longya et al 2020), insect (Wang et al 2020) andanimal (ElAzim et al 2019).…”