Agrobacterium- mediated Genetic Transformation of oilseed Brassica juncea(L.)

Brassica is an important oilseed crop in Bangladesh. The available Brassica varieties cultivated in Bangladesh are susceptible to many diseases and pests specially, with fungal diseases. In this context, an alternative to trait improvement especially disease resistant variety would be evolved by applying biotechnological approaches like genetic transformation. So, the present investigation was carried out for the development of Agrobacterium-mediated genetic transformation system for oilseed Brassica grown in Bangladesh. Prior to the transformation an efficient in vitro regeneration protocol was developed for two varieties of Brassica juncea namely, BARI Sarisha-11 and BARI Sharisha-16. The best shoot regeneration was obtained from hypocotyl explants using MS medium supplemented with 2.0 mg/l BAP and 0.2 mg/l NAA. MS medium hormone was found to be effective in inducing roots. Three gene construct (LBA4404/pBI121, LBA4404/ pCAMBIA2300polyA AFPFP, EHA105/pGII-pSOUP-VST-N-CHITIN) of Agrobacterium were used for transformation experiments. Transformation frequency regarding the recovery of shoots for BARI Sarisha-11 and BAR Sarisha-16 using  gene construct I was 0.84% and 0.96% respectively, while that was 0.63% and 0.78% respectively in case of construct III. The stable integration of the putatively transformed shoots developed by using EHA105/pGII-pSOUP-VST-N-CHITIN (containing bar and chitinase gene) was confirmed through PCR analysis. Keywords: Oilseed Brassica; In vitro Regeneration; Genetic Transformation Bangladesh

Antiferromagnetic Heisenberg model on anisotropic triangular lattice in the presence of magnetic field

We use Schwinger boson mean field theory to study the antiferromagnetic spin-1/2 Heisenberg model on an anisotropic triangular lattice in the presence of a uniform external magnetic field. We calculate the field dependence of the spin incommensurability in the ordered spin spiral phase, and compare the results to the recent experiments in Cs$_{2}$CuCl$_{4}$ by Coldea et al. (Phys. Rev. Lett. 86, 1335 (2001)).Comment: 4 pages with 4 figures include

Agrobacterium-mediated genetic transformation in lentil (Lens culinaris Medik.) followed by in vitro flowering and seed formation

Genetic transformation system was developed for two microsperma varieties of lentil (Lens culinaris Medik.), namely Bari Masur-4 (BM-4) and Bari Masur-5 (BM- 5) using Agrobacterium tumefaciens strain LBA4404 harbouring binary plasmid pBI121, containing GUS and nptII genes. Three different types of embryo explants, namely cotyledonary node (CN), decapitated embryo (DE) and cotyledone attached decapitated embryo (CADE) were used. Highest GUS positive expression was found in DE followed by CADE as detected by transient assays. Following Agrobacterium infection CADE showed better response in developing multiple shoots on MS supplemented with 2.22 μM BAP, 2.32 μM Kn, 0.29 μM GA3 and 30.35 μM tyrosine. Selection of the transformed shoots was carried out by gradually increasing the concentration of kanamycin up to 200 mg/l. Transgenic lentil shoots were produced with an overall frequency of 1.009%. In vitro rooting appeared to have a limitation in obtaining complete plantlets in lentil, therefore in vitro flowering and seed formation were induced in transformed shoots of lentil with a view to recovering of the transgenic progenies. GUS positive shoots were found to produce in vitro flowers and pods on half-strength MS containing 98.4 μM IBA and 2.69 μM NAA. Expression of gene was detected in various tissues of the transformed shoots. Stable integration of GUS gene was also confirmed through PCR analysis

TDZ-induced direct shoot organogenesis and somatic embryogenesis on cotyledonary node explants of lentil (Lens culinaris Medik.)

An efficient and simple procedure for inducing high frequency direct shoot organogenesis and somatic embryogenesis in lentil from cotyledonary node explants (without both the cotyledons) in response to TDZ alone is reported. TDZ at concentration lower than 2.0 μM induced shoot organogenesis whereas at higher concentration (2.5–15 μM) it caused a shift in regeneration from shoot organogenesis to somatic embryogenesis. The cotyledonary node and seedling cultures developed only shoots even at high concentrations of BAP and TDZ, respectively. TDZ at 0.5 and 5.0 μM was found to be optimal for inducing an average of 4–5 shoots per cotyledonary node in 93 % of the cultures and 55 somatic embryos in 68 % of the cultures, respectively. The somatic embryos were germinated when transferred to lower TDZ concentration (0.5–1.0 μM). The shoots were rooted on MS basal medium containing 2.5 μM IBA. The plantlets were obtained within 8 weeks from initiation of culture and were morphologically similar to seed-raised plants. The possible role of stress in thidiazuron induced somatic embryogenesis is discussed