Performance of polyvoltine silkworm Bombyx mori L. on different mulberry plant varieties

Five cultivated mulberry plant varieties, BSRM‐34, BSRM‐56, BSRM‐57, BSRM‐58 and BSRM‐59, were used to evaluate the effects of plant variety on larval and cocoon characteristics of mulberry silkworm Bombyx mori L. Silkworm larvae undergo their entire larval periods on leaves of mulberry varieties. Different larval characteristics of larval weight, larval length and larval breadth were measured in different growth stages. After rearing, the fifth instar larvae were transferred into a mountage (Chandraki) structure for cocoon rearing for spinning and cocoon production. The cocoons were then harvested and different cocoon characteristics like cocoon weight, shell weight and shell percentage; and other characters like pupal weight and effective rate of rearing were measured. The results showed statistically significant differences among different varieties on larval and cocoon characteristics. The highest performance was observed by feeding the variety BSRM‐34 in respect of the average weight of 10 mature larvae (40.5 g), single mature larval length (7.6 cm) and breadth (1.0 cm), single cocoon weight (1.4 g), shell weight (0.2 g) and pupal weight (1.2 g) while the average performance was recorded by feeding varieties BSRM‐57 and BSRM‐59. The poorest performance was showed by feeding the variety BSRM‐56 (in case of larval characters) and BSRM‐58 (in case of cocoon characteristics). These two varieties also showed the poorest performance for silk yield. Through comparing all the above parameters it was concluded that BSRM‐34 is the best mulberry variety and it is recommended that Bangladeshi farmers adopt that variety for better yield of silk.     

Cytotaxonomical study in Brazilian species of Solanum, Lycianthes and Vassobia (Solanaceae)

Solanum comprises about 1,400 species of shrubs, trees and vines. This group is cytogenetically interesting because it possesses karyotypes apparently conserved in chromosome number and shape, but with diversity in the repetitive DNA. The objective of this study is to characterize 16 species of Solanum and two species of closely related genera (Lycianthes australe and Vassobia breviflora) using cytogenetic parameters. All the species presented 2n = 24, confirming previous chromosome counting. Additionally, nonreticulated nuclei, proximal condensation in prophase-metaphase and little variation in the karyotype symmetry were observed. Solanum corymbiflorum exhibited chromosomes approximately three times bigger in relation to the other species. GC-rich heterochromatin was preferentially located at terminal regions and AT-rich blocks always appear in the centromeric regions. The 45S rDNA sites were coincident with C/CMA₃ ⁺ regions (satellites) and found in just one pair, except in S. corymbiflorum which presented two pairs. FISH with 5S rDNA showed signals in the paracentromeric region of one chromosome pair, except in S. trachytrichium and S. gemellum which showed two hybridization signals. The results point out to different ways of karyotype differentiation in Solanum and closely related genera and bring important issues on the value of the cytogenetical information for taxonomic studies.     

Biofloc Technology: Emerging Microbial Biotechnology for the Improvement of Aquaculture Productivity

With the significant increases in the human population, global aquaculture has undergone a great increase during the last decade. The management of optimum conditions for fish production, which are entirely based on the physicochemical and biological qualities of water, plays a vital role in the prompt aquaculture growth. Therefore, focusing on research that highlights the understanding of water quality and breeding systems’ stability is very important. The biofloc technology (BFT) is a system that maximizes aquaculture productivity by using microbial biotechnology to increase the efficacy and utilization of fish feeds, where toxic materials such as nitrogen components are treated and converted to a useful product, like a protein for using as supplementary feeds to the fish and crustaceans. Thus, biofloc is an excellent technology used to develop the aquaculture system under limited or zero water exchange with high fish stocking density, strong aeration, and biota. This review is highlighted on biofloc composition and mechanism of system work, especially the optimization of water quality and treatment of ammonium wastes. In addition, the advantages and disadvantages of the BFT system have been explained. Finally, the importance of contemporary research on biofloc systems as a figure of microbial biotechnology has been emphasized with arguments for developing this system for better production of aquaculture with limited natural resources of water.Key words: biofloc, BFT, aquaculture, microbes, water quality, wastes     

CYTOGENETIC STUDIES OF SOME HYPOCHOERIS SPECIES (COMPOSITAE) FROM BRAZIL

Karyotypes of nine Brazilian taxa of genus Hypochoeris were studied utilizing root-tip mitotic metaphases. Two distinct groups were found. One group includes six species that showed high asymmetric bimodal karyotypes, while the second group has two species that have a karyotype similar to those observed in European species. All the species have karyotypes with 2n = 8 that are very uniform within each group, with only small morphological differences. Nucleolar organizing region and C-band patterns are shown for H. brasiliensis.     

Suction force variation in double-hybrid maize as a function of soil moisture

In experiments with double-hybrid maize grown in the field and in a greenhouse, we analysed the value of the suction force as related to the regime of irrigation. The results showed that the level of water supply to the plants is in good connection with the value of the suction force and the coefficient H (the relative degree of water saturation of the cells) analysed at the same time. In the case of the 2 hybrids under investigation the highest value of coefficient H was found to be between 35–48. The data indicate that the use of these two indices should take part in a physiological method for the settlement and the application of water rules in irrigation.     

IGS sequences in Cestrum present AT- and GC-rich conserved domains,with strong regulatory potential for 5S rDNA

Molecular Biology Reports - The 35S and 5S ribosomal DNA (rDNA) organized in thousands of copies in genomes, have been widely used in numerous comparative cytogenetic studies. Nevertheless, several...