RESUMEN
White clover (Trifolium repens) is an allotetraploid pasture legume widely used in moist temperate climates, but its vulnerability to drought, grazing pressure and pests has restricted its wider use. A related species, Caucasian clover (Trifolium ambiguum), is a potential source of resistances to drought, cold, grazing pressure and pests that could potentially be transferred to white clover by interspecific hybridization. Although direct hybridization has been achieved with difficulty, the hybrids have not been easy to backcross for introgression breeding and no interspecific chromosome recombination has been demonstrated. The present work shows that interspecific recombination can be achieved by using Trifolium occidentale, one of the ancestral parents of T. repens, as a bridging species and that large white clover breeding populations carrying recombinant chromosomes can be generated. A 4x hybrid between T. ambiguum and T. occidentale was crossed with T. repens and then backcrossed for two generations. Five backcross hybrid plants with phenotypes appearing to combine traits from the parent species were selected for FISH-GISH analyses. Recombinant chromosome segments from T. ambiguum were found in all five plants, suggesting that recombination frequencies were significant and sufficient for introgression breeding. Despite early chromosome imbalances, the backcross populations were fertile and produced large numbers of seeds. These hybrids represent a major new resource for the breeding of novel resilient forms of white clover.
RESUMEN
The study was aimed to investigate microencapsulation of theophylline using different ratios of eudragit S 100 as wall material by the emulsion solvent evaporation technique. The release profiles, effect of stirring speed and different pH of dissolution medium on release profiles and stability were also studied. Various formulations of microcapsules were compressed in to tablets. In vitro dissolution studies indicated that the rate of drug release was reduced with an increase in the amount of Eudragit S 100. Moreover, the release data of various formulations were fitted to Zero order, First order, Higuchi, Hixson Crowell and Korsmeyer Peppas kinetic models. It was observed that the release of drug from all the formulations followed Higuchi's kinetic model as its value of coefficient of determination is greater than that of others. The release profiles of the test formulation in distilled water and various pH media were compared and decreased release rate was seen at lower pH i.e. pH 1.0. Slight or no change was apparent in the release rate at higher stirring speed compared to lower stirring speed. No significant changes were also observed in the drug release profiles of test tablets stored at different temperatures. Test tablet (F2) was found to produce similar and sustainable release rate compared to commercial product, Quibron-T/SR tablet on the basis of their T(70%). Similarly, f(2) values of reference versus F2 is 66.98 which show less difference between these two as compared to the comparison of reference with F1 and F3.
