Challenges of In Vitro and In Vivo Agrobacterium-Mediated Genetic Transformation in Soybean

Agrobacterium tumefaciens-mediated genetic transformation of plants is a natural process. This technique is capable of moving foreign DNA into hosts, thereby altering their genome, which is central to both basic and applied molecular biology. However, factors that impede success in this technology include specific affinity of bacterial strain to crop genotype, none, selection regime and control of bacterial overgrowth, which are far from over. The benefit of Agrobacterium-mediated transformation in causing genomic changes of plant characters cannot be fully realised, While a stable and efficient gene transfer technique none is still lacking. Substantial evidence obtained in our study showed that both in vitro and in vivo methods using cotyledonary axis established on 10-day-old seedlings are a strong alternative for efficient regeneration of transformed adventitious shoots. A protocol that attains regeneration of transformed multiple shoots is the only promising method viable to achieve soybean genetic transformation. High shoot regeneration of 60.0%, 63.3% and 76.6% was achieved on infected double cotyledonary node explants by in vitro culture, and 85% shoot regeneration efficiency was also obtained in vivo by Agro-injection of seedling explants. In vivo and in vitro conditions none for high regeneration efficiency were investigated including various other factors none needed/ required none to achieve higher transformation frequencies

Antibacterial activity of plants that are used in the treatment of heartwater in livestock and the isolation and identification of bioactive compounds from Petalidium Oblongifolium and Ipomoea adenioides

The general antibacterial activity of Drimia delagoansis, Petalidium oblongifolium and Ipomoea adenioides was determined using selected Gram-positive and Gram-negative bacteria. Only extracts or compounds with high antibacterial activity were then tested against the causative agent of heartwater, Ehlrichia ruminantium, since the latter requires specialised culturing conditions. The crude aqueous extract of D. delagoansis had low antibacterial activity with its highest MIC against Gram-negative bacteria being 20.0 mg ml-1 while the crude methanolic extracts of P. oblongifolium and I. adenioides had their highest antibacterial activity against Gram-negative bacteria at MIC's of 5.0 and 10.0 mg ml-1 respectively. Two compounds were isolated and identified from I. adenioides and an unidentified one was isolated from P. oblongifolium. The two compounds from I. adenioides proved to be caffeic acid with MIC's of 0.8 and 1.0 mg ml-1 against Gram-positive and Gram-negative bacteria respectively; and ethyl caffeate with MIC's of 0.4 and 1.0 mg ml-1 against Gram-positive and Gram-negative bacteria respectively. Synergism between the two compounds increased the respective MIC's to 0.4 and 0.2 µg ml-1 against Gram-positive and Gram-negative bacteria. The unidentified compound isolated from P. oblongifolium had a very low MIC of 2.5 µg ml-1 against E. ruminantium.Thesis (PhD (Botany))--University of Pretoria, 2007.Plant Scienceunrestricte

Pollination in Plants

Plants are the basic source of food for both humans and animals. Most of the food is made of fruits and seeds. For these to be formed, pollination must first take place. This process is the transfer of pollen grains from the anther, which is the male structure of the flower, to the sigma on the female structure of the flower. The transfer process requires agents to be carried out. The agents can be either biotic or abiotic. Nature perfected this arrangement between the pollination agents and the plants. As ecosystems and agricultural systems are changing, this balanced arrangement becomes disturbed. This makes it necessary that pollination systems be studied so that necessary measures can be undertaken to ensure productivity. The chapters of this book present results in research undertaken to improve productivity in crops such as Actinidia chinensis (the kiwifruit), Theobroma cacao (cocoa), and Manicaria saccifera (a tropical forest palm). Some results are presented on tests to check the viability of pollen grains and the delivery of sperm cells through pollen tubes to the embryo sac. These results can serve as guidelines to any person seeking to improve pollination and productivity or to check the efficiency on pollination in ecosystems or agricultural production systems

The Influence of Seed Viability on the Germination and In Vitro Multiple Shoot Regeneration of Soybean (<i>Glycine max</i> L.)

The moisture status of seeds is usually high during the period of harvest and deterioration (loss of viability) starts to occur when seeds are stored for longer periods. In the present study, soybean seeds were evaluated using a standard germination test, in vitro germination, and for efficient multiple shoot induction, following storage under ambient conditions for 0, 3, 6 and 9 months. Results showed that seeds stored for more than 3 months had reduced moisture content and decreased germination percentages in LS677, LS678, Dundee, Peking, TGx1740-2F and TGx1835-10E of the tested genotypes. In particular, seeds stored for 9 months showed significantly poor seed viability and less than 50% overall seed germination (Dundee&#8212;42%, LS678&#8212;49%, TGx 1740-2F&#8212;44%, TGx 1835-10E&#8212;48%), except for LS677 and Peking, with 52 and 55%, respectively. The efficiency of multiple shoot induction also decreased with prolonged seed storage, with all genotypes recording an overall decline from about 96% to 40% regeneration efficiency within 9 months. The results obtained clearly indicated that high germination rates and efficient in vitro shoot induction depended largely on seed viability and storage duration, and significantly differed according to genotypes