Characterization and genetic relationships among Brazilian biotypes of Schizaphis graminum (Rondani) (Hemiptera: Aphididae) using RAPD markers

Abstract

PALAVRAS-CHAVE: Variabilidade genética, pulgão-verde-dos-cereais, relação inseto-plantaABSTRACT -The greenbug Schizaphis graminum (Rondani) is one of the most important cereals pests in the world. Within populations of this species, several biotypes, which are clones that share same virulence relationships with cultivated plants, can be distinguished. Molecular markers have been used to genetically characterize insect populations because they are fast and cost effective. In order to find RAPD markers to identify Brazilian S. graminum biotypes, nineteen clonal populations of three biotypes (B, C and E) from Brazil and three clonal populations from the U.S. were examined. Eighteen primers were used to analyze the material, but only six primers revealed polymorphisms and among those, three produced diagnostic band profiles that allowed biotype characterization. Using Jaccard Similarity Index and UPGMA clustering method it was possible to show that biotype B is genetically very distinct from C and E, which are closely related to each other. The biotype C showed the greatest genetic diversity, while biotype E was the least diverse. Analysis of Molecular Variance (AMOVA) showed that genetic variance among clonal populations belonging to the same biotype is smaller than among clonal populations grouped according to their geographical similarity.

Variabilidade genética de Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae) em cultivos olerícolas em São Luís, MA

“…Segundo Lopes-da-Silva (2004), o conhecimento da existência de biótipos em insetos de importância agrícola é fundamental para o manejo integrado de pragas, pois muitos problemas com pragas agrícolas são também problemas evolutivos, e compreender como ocorre a evolução em sistemas agrícolas pode facilitar a implementação de estratégias de controle (Via 1990). Os resultados obtidos no presente trabalho mostraram, principalmente, alta dispersão do biótipo B de B. tabaci em São Luís, MA.…”

Temporal genotypic diversity of Schizaphis graminum (Rondani 1852) (Hemiptera: Aphididae) in a black oats (Avena strigosa) field

“…Chi-square tests (X 2 ) were done to test significance of frequency variation between the two more abundant genotypes. To identify the biotypes present in the field at the end of the sampling period, a rapid bioassay for virulence was carried out using the lesion technique methodology described in Lopes-da- Silva et al (2004). Ten clonal lineages originated by the females collected in August were reared on wheat Embrapa-16, which had the cultivar Amigo in its genetic background (biotype C-resistant and biotype E-susceptible).…”

“…The greenbug, Schizaphis graminum (Rondani 1852), is one of the most important cereal pests in the world. Defining biotypes as part of an aphid population that shares the same virulence to cultivated plants, several biotypes can be distinguished within populations of this aphid species (Lopes-da-Silva et al, 2004). S. graminum has been the target of research work aimed at understanding the biotypes evolution (Anstead et al, 2002), but despite the economic importance as a pest of cultivated grasses, aspects of its population dynamics have been neglected, mainly in South America.…”

“…According to this hypothesis, in southern Brazil, the infestation of cereal crops arises mainly by the colonizers from northern regions, which implies in extinctions and recolonization events. As S. graminum populations have detectable genetic variation at geographic scale (Lopes-da-Silva et al, 2004), it could be assumed that high levels of aphid migration would result in temporal genetic variation locally. However, Lopes-da-Silva et al (2004) considered that clones living on wild grasses nearby to cereals fields were the main colonizers, and most likely the sole colonizers at least in early stages of crop development.…”

“…As S. graminum populations have detectable genetic variation at geographic scale (Lopes-da-Silva et al, 2004), it could be assumed that high levels of aphid migration would result in temporal genetic variation locally. However, Lopes-da-Silva et al (2004) considered that clones living on wild grasses nearby to cereals fields were the main colonizers, and most likely the sole colonizers at least in early stages of crop development. In order to test the hypothesis that migration was the main variable that affected genetic diversity of S. graminum, in this work, RAPD molecular markers was used to evaluate the genetic diversity among S. graminum clones collected at same place within a complete phenological cycle of black oats as RAPD markers have been useful to detect genetic variability within and among the species of same genus (Crochemore et al, 2003).…”