Abstract:
Yam (Dioscorea spp.) in Kenya is a neglected crop, despite having a lot of potential for providing food security and income to resource-poor farmers. Yam tubers are nutritionally rich and a major source of dietary fiber, carbohydrates, vitamin C and essential minerals. Yam production is limited by several viral and fungal diseases, pests such as nematodes and poor soil fertility. Genetic improvement of yam through conventional breeding is challenging due to long growth cycle, dioecious and poor flowering nature, polyploidy, vegetative propagation and heterozygous genetic background barriers. Biotechnology offers a wide range of opportunities that can help yam become a better crop for a constantly changing world. The objective of this study was to develop an Agrobacterium-mediated transformation of yam (Dioscorea rotundata). Two cultivars of D. rotundata were transformed using Agrobacterium tumefaciens strains EHA105 and LBA4404 harboring the binary vectors containing β-glucuronidase (GUS) reporter gene. Shoots were regenerated on induction and elongation media with appropriate concentrations of antibiotics and subsequently rooted on medium supplemented with selection agent. Polymerase chain reaction (PCR) analysis and histochemical assay for GUS activity of plant tissues were used to confirm success of transformation. Expression of gusA gene in transgenic plants was also checked by reverse-transcriptase (RT)-PCR analysis. Transformation efficiency varied from 10.2% to 18.2% depending on the cultivars, selectable marker genes, and the Agrobacterium strain used for transformation. We report an efficient and reproducible protocol for genetic engineering of D. rotundata, which provides a useful platform for future improvement of this economically important food and nutritional security crop.
