Dissimilaridade genética de linhagens de Trichogramma Westwood (Hymenoptera: Trichogrammatidae) através de marcadores moleculares ISSR

Abstract

-Demands for sustainable agricultural systems have forested the development of biological control techniques, such as the use of the egg parasitoid Trichogramma Westwood. However, the arduous identification of the parasitoid at the species level, due to the tiny size and the morphological similarities is an obstacle to increasing its use. Molecular markers are useful to reach the specimen genome and avoid environmental effects that could misguide identification. Several molecular markers techniques are available and the ISSR technique has been used to differentiate close individuals, due to its high polymorphism level, reproducibility and low cost. The objective of this study was to measure the level of genetic differentiation among five lines of Trichogramma, using ISSR markers: three belonging to the species T. pretiosum Riley, one to T. atopovirilia Oatman & Platner and one to T. bruni Nagaraja. Morphological identification of the parasitoids was conducted at ESALQ/USPPiracicaba, SP. After DNA removal and standatization, PCR reactions were performed with 26 ISSR primers; 11 of them were selected because they presented greater polymorphism and consistency. Molecular data were converted into a binary matrix and analyzed (NTSYS v. 2.1). The 11 primers produced 172 polymorphic sections. Genetic similarity ranged from 19% to 96%, showing that the ISSR technique can efficiently identify DNA polymorphism in Trichogramma. Results also indicate important inter and intra-specific variations among the parasitoid lines.KEY WORDS: Molecular biology, microhymenopteran, identification, biological control RESUMO -A demanda por processos agrícolas racionais, em detrimento da utilização de estratégias convencionais, tem contribuído para o desenvolvimento de técnicas de controle biológico, como a utilização de parasitóides de ovos do gênero Trichogramma Westwood. Um entrave para sua utilização é a dificuldade na identificação das espécies, devido ao diminuto tamanho e à similaridade morfológica. Os marcadores moleculares acessam o genoma, evitando o efeito ambiental e conseqüentemente erros de identificação. Várias técnicas estão disponíveis e a técnica ISSR vem sendo empregada para a diferenciação rápida entre indivíduos próximos, devido ao elevado grau de polimorfismo, reprodutibilidade e baixo custo. Este trabalho objetivou mensurar o nível de diferenciação genética de linhagens de Trichogramma, mediante o emprego da técnica de ISSR. Cinco linhagens foram estudadas: três da espécie T. pretiosum Riley, uma da espécie T. atopovirilia Oatman & Platner e uma da espécie T. bruni Nagaraja. A identificação morfológica dos parasitóides foi realizada na ESALQ/ USP, Piracicaba, SP. Após a extração do DNA e sua padronização, realizaram-se as reações de PCR utilizando-se 26 marcadores ISSR, dos quais 11 foram selecionados por apresentarem maior polimorfismo e consistência. Os dados moleculares foram transformados em matriz binária e analisados pelo programa estatístico NTSYS v. 2.1. Os 11 marcadores utilizados geraram 172 banda...

Determining the genetic stability of micropropagated sugarcane using inter-simple sequence repeat markers

“…ISSR markers represent a simple technique with a high degree of polymorphism, reproducibility, and low cost. One example of an ISSR is microsatellites, which are very applicable in genetic studies of economically important organisms (Borba et al, 2005;Toppa and Jadoski, 2013). The dendrogram was built from the amplification products obtained using UBC oligonucleotides of ISSR type, using the UPGMA clustering method, based on the addition of the coefficient of similarity as defined by Jaccard.…”

Genetic variability of Dactylopius opuntiae (Homiptera, Dactylopiidae) on forage cactus in northeast Brazil

“…(Coleoptera, Bruchidae) and found 52 polymorphic fragments and an average polymorphism of 83.82% but low levels of genetic differentiation. In contrast, Borba et al (2005), studying strains of Trichogramma Westwood (Hymenoptera: Trichogrammatidae), detected a high percentage (96%) of polymorphism. Among the insects widely investigated by molecular techniques, the silkworm B. mori is a prominent model system and recognized in several countries, which contributes to the improvement of breeds of this insect (Bakkappa et al, 2011).…”

Molecular identification of Trichogramma species from regions in Brazil using the sequencing of the ITS2 region of ribosomal DNA

“…Due to the importance of its use, to succeed in a biological control program with the Trichogramma species, correct identification is essential, so one can check if they respond to the climatic conditions of the region and culture that they will be applied to (Borba et al, 2005).…”

“…However, in some cases the identification is difficult due to the absence of males in thelytokous species infected by bacteria of the genus Wolbachia, the presence of cryptic species and the small size of the individual (Almeida and Stouthamer, 2003;Borba et al, 2005). A more recent method, molecular biology, has been widely used in the taxonomic identification of diverse groups of insects (Borba et al, 2005).…”

“…Species particularly difficult to identify with the use of traditional taxonomic techniques may have their identities clarified using molecular sequencing techniques or sequence length polymorphism generated through the techniques of molecular markers (Borba et al, 2005).…”