Variabilidade genética de raças e híbridos simples de Bombyx mori L. do banco de germoplasma da Universidade Estadual de Maringá

• Autor(a) principal: Munhoz, Roxelle Ethienne Ferreira
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1347
• topic: Bombyx mori; Melhoramento genético; Marcadores ISSR; Bicho da seda; Brasil.; Silkworm; Genetic breeding of Bombyx mori; ISSR markers; Genetic breeding of Bombyx mori; ISSR markers; Brazil.; Ciências Agrárias; Agronomia

In the present study we evaluated, using genetic and statistical methods, superior genotypes for genetic breeding program of Bombyx mori (silkworm), from germplasm bank of Universidade Estadual de Maringá (UEM). For that, four distinguished experimental designs were carried out separately, using different biological material, and independent objectives and analysis methods. For the first assay, B. mori strains were evaluated regarding their genetic and yield characteristics. This analysis was determined by herdability coefficient and correlation analysis between biological and yield characteristics important for cocoon production. The results demonstrated that silk content has low heritability and no significant correlation was observed between the evaluated characteristics. For the second assay, 32 hybrid combinations were made between selected parents by a previous productivity analysis and a commercial hybrid was used as control, considering that the results were submitted to variance analysis and Scott- Knott test. Strains HA-A and C24-2 were identified by Mahalanobis' distance as the most divergent ones, thus, we obtained the best hybrids from the following crosses: C122-B x HA-A and HA-A x C24-2. The third experimental design used a non-parametric statistical method based on multiple evaluation index to identify superior genotypes of UEM's germplasm bank. A total of 34 genotypes were evaluated and a scaled interpretation ranking based on five quantitative variables was established. According to the results, the three most promising genotypes are simple hybrids derived of female parent that belongs to matrices of Japanese origin. The advantage of this evaluation statistical methodology is the creation of a single index to classify genotypes. However, it can also show disadvantage to not consider the significant differences among themselves. The fourth assay, conducted with ten matrices, selected as candidates to compose the elite silkworm genetic breeding program from UEM, were investigated regarding their genetic diversity through ISSR molecular markers. For these experiments, nine primers were chosen to run reactions, and produced 109 DNA fragments that varied from 200 base pair (bp) to 2,000bp; revealing 100% of polymorphism among the populations. The results revealed that different heterotic groups were formed based on clustering analyses. Parental races B106, M12-2, M11-2 and J1 were allocated in group I; whereas C24, C25, M18 and B82 composed group II. On theother hand, only race M19-2 composed group III, due to discrepancy observed on clustering analyses obtained by Nei's distance and Jaccards' Coefficient. All experimental assays conducted and used methodologies aimed for the progress of B. mori (silkworm) genetic breeding program of UEM.