Morphologic and genetic analysis for geographic populations of greenbug Schizaphis graminum (Hemiptera: Aphididae) in Egypt

Abstract

Greenbug Schizaphis graminum is one of widespread aphid species in most wheat growing regions of Egypt that causes severe damages to crops. Studying morphological and genetic variations within insect pest populations are essential for identifying species and population distinctions and subsequently developing integrated pest management. Sixteen geographic populations of S. graminum were sampled from wheat fields in Egypt. Specimens were characterized by morphological screening for 19 quantitative morphological characters, examination of genomic DNA polymorphism with 11 inter simple sequence repeats (ISSR) primers, and measuring melting temperature (Tm) for cDNA of the mitochondrial cytochrome oxidase subunit I (COI) gene. The greatest morphological variance was observed among aphid populations from Domiata, El-Menia, and Beni-Suif. Geographic location of sampled populations had significant effect on melting temperature of the COI gene. The highest value was observed in populations from Assuit and the lowest from El-Gharbia. Populations from El-Monofia and Kafer El-Shikh were most similar based a combination of COI melting temperatures and quantitative morphological features. Tested ISSR primers showed a polymorphism rate of 49.43% among geotypes. The UBC814 primer recognized a population-specific band of 950 bp that characterized the Domiata population. Moreover, UBC811 and UBC868 primers generated bands with molecular sizes 440 and 340 bp characterizing only populations of Lower and Upper Egypt, respectively. ISSR analysis revealed that geographic populations from El-Behera, Domiata, and Kafer El-Shikh are genetically homologous with identities of 90.4–90.7%. In contrast, populations of Luxor and El-Behera are genetically analogous. Finally, a molecular branching key was constructed to discriminate among tested populations.