Phetole Mangena

By Phetole Mangena, Phatlane William Mokwala and Roumiana Vassileva Nikolova

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.

Part of the book: Soybean

By Phetole Mangena

Water stress is one of the most important physiological stress factors that adversely affect soybeans in many critical aspects of their growth and metabolism. Soybean’s growth, development and productivity are severely diminished, when soil or cell water potential becomes inadequate to sustain metabolic functioning. However, little has been done to gather comprehensive information regarding the specific changes that occur in water-stressed plants at the anatomical and morphological level. In this study, deviations in root growth, shoot growth, stomatal conductance, yield components and anatomical features are reported. Treatments with two levels of water stress imposed by reducing irrigation (once in 7 days or once in 15 days) revealed that, all cultivars (Dundee, LS 677, LS 678, TGx 1740-2F, TGx 1835-10E and Peking) were highly susceptible to prolonged water stress, exhibiting severe dehydration and death. A 15.0 and 30.0% survival frequency was obtained in plants irrigated once in 7 days; LS 677 and Peking, respectively. Unlike many other stresses, water deficit did not only affect the density of stomata, but, photosynthesis was affected by the lower levels of tissue CO2. These results suggest that, balanced biochemical, physiological, anatomical and morphological regulations are necessary for increased growth and yields in soybean.

Part of the book: Plant, Abiotic Stress and Responses to Climate Change

By Phetole Mangena and Phatlane William Mokwala

Part of the book: Pollination in Plants

By Phetole Mangena

An efficient and reproducible plant regeneration protocol is essential for genetic manipulation of important crops in vitro through Agrobacterium-mediated genetic transformation. However, the establishment of such a procedure for recalcitrant legumes like soybean is still a major challenge. Genotype specificity, culture conditions and inefficient recovery of transgenic microshoots are some of the most important factors which requires optimisation before an efficient system of regeneration can be developed. The purpose of this chapter was to provide a review, and report on the varied responses obtained during the assessment of factors that cause recalcitrance during genetic transformation of soybean. Agrobacterium infected double cotyledonary-node explants were tested on MS basal culture medium containing combinations of cytokinins-auxins, as well the different concentrations of antibiotics for callus and shoot proliferation. The study showed that, the efficiency of microshoots and callus induction varied widely between cultures and among the genotypes. About 1.0–20.0 and 5.0–20.0% of callus and shoot induction frequency were obtained on cotyledonary explants transformed with Agrobacterium compared to more than 60% efficiency obtained in the controls, respectively. This study revealed that, there are some neglected factors playing a crucial role in genetic manipulation, which require optimisation before genetic transformation and in vitro regeneration of transgenic plants could be achieved.

Part of the book: Transgenic Crops