Cytogenetic and Molecular Analysis Aspects on some Local Romanian Bombyx mori Races

Abstract

SUMMARY About 3000 distinct genotypes of Bombyx mori - an excellent model for Genomicssituates this species on second place after Drosophila , as an insect model for studying heredity which started in Japan, at the beginning o f XIX th century. The appearance of some local B. mori races in Romania imposed the necessity of studying them under cytogenetic and molecular aspects for their precise identification. The analyses done on six Romanian B. mori races employing some classic cytogenetics methods (aceto-carmine, DAPI and Giemsa staining) have demonstrated normal meiotic and mitotic chromosomal complements (n=28; 2n=56) as well as in some cases hypoand hyper-ploidy. Using TEM (transmission electron microscopy) technique, the synaptonemal complexes in pachytene-diplotene stages were detected. In silk-glands of IV th stage larvae, the polyteny phenomenon was described associated with the ribosomal gene amplification process visualized as a plethora of R NPs (ribonucleoprotein particles) of different sizes and shapes. The chromosomal bivalen ts in different stages of meiosis, with a typical structure and behavior, were identified. Optimization and implementation of modern molecular methods, as well as the study of some molecular markers (RAPD-RFLP) allowed us to obtain different electrophoretic patterns valuable for differentiating and identific ation of the studied races. All electrophoretic patterns obtained from PCR-RAPD reaction with OPA4 , OPA7 , OPA8 , P1 , P4 and P5 primers followed by RFLP reaction using HaeIII enzyme proved to be different, so that each studied race could be discr iminated. Applying molecular methods can be helpful in the br eeding process of silkworms assisted by classical and modern molecular genetics approaches.