Roxelle Ethienne Ferreira Munhoz

Biological and molecular characterization of silkworm strains from the Brazilian germplasm bank of Bombyx mori.

Brazil has only one public genetic pool of Bombyx mori strains, which was established in 2005 at Universidade Estadual de Maringá, Maringá, Paraná State. This genetic bank has been maintained, and the strains have been characterized using genetic and morphological tools. The quantitative and qualitative traits, directly or indirectly related to productivity, were evaluated in 14 silkworm strains. In addition to biological and productivity analyses, DNA markers related to susceptibility to the B. mori nucleopolyhedrovirus (BmNPV) were analyzed. BmNPV is a major cause of production loss and is a serious problem for Paraná sericulture. The silkworm strains from diverse geographic origins were found to have different characteristics, including body weight, larval stage duration, cocoon weight, and other biological traits. In terms of productivity, the raw silk percentages were almost uniform, with an overall average of 16.28%. Overall, the Chinese strain C37 gave the best performance in many of the quantitative traits, and it surpassed the other strains in productivity traits. Therefore, it can be used as one of the strains that compose the elite germplasm for silkworm breeding programs. Additionally, genetic molecular markers were efficient in discriminating between B. mori strains that had been identified based on their geographical origin. We found that all Japanese strains produced a 400-bp molecular marker that has been associated with susceptibility to BmNPV.

Genetic diversity analysis with RAPD linked to sex identification in the sugar cane borer Diatraea saccharalis.

Diatraea saccharalis is an insect that causes considerable losses in the sugar cane crop. Our aim was to contribute to the knowledge of the biology of D. saccharalis, with the report of DNA fragments involved in the differentiation between the male and female of this species using the RAPD sex molecular marker GyakuU-13, which is specific for the W chromosome of Bombyx mori. Another point evaluated in this study was the genetic diversity of a D. saccharalis population maintained by inbreeding in a laboratory culture. The profile of sex-specific fragments was analyzed, and the genetic variability of this population was estimated. An analysis of the molecular markers showed only one fragment, of approximately 700 bp, that could be considered as a female sex marker in D. saccharalis.