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A wide range of legume species have been genetically transformed and the transformants regenerated to provide novel genotypes. The methods used for transformation include the use of Agrobacterium tumefaciens, A. rhizogenes, particle bombardment and electroporation. Although Agrobacterium-based methods using a wide variety of tissue explants have been the most widely used, generally they yield low rates of transformation (0.1–5%). In planta techniques, either with Agrobacterium or electroporation of intact meristems, hold the promise of much higher frequencies and more simple means of regeneration of transformants. Methods have been developed for soybean, pea, cowpea, moth bean, common bean, black gram, groundnut, lentil, narrow-leafed lupin, yellow lupin, winged bean, broad bean, narbon bean, pigeon pea, grass pea and chickpea among the pulses and for a number of medics and clovers, alfalfa, Townsville stylo, sainfoin and birdsfoot trefoil among pasture species. In many cases viable plants and seed have been recovered and the transformations are stable. Most commonly the reporter gene for s-glucuronidase (gus), or genes for antibiotic resistance (npt, hpt) have been used as selectable markers. More recently genes conferring tolerance to herbicides (eg bar or pat for glufosinate [Basta] or aro A and cp4/gox for glyphosate [Roundup]) have proven to be more effective. These genes have also provided a basis for engineering novel herbicide-tolerant cultivars of a number of crop species. Transformations to enhance the nutritional quality of grain or herbage, or to insert genes associated with nodule function have also been generated. A detailed summary of procedures developed for the A. tumefaciens-mediated transformation of narrow-leafed lupin (Lupinus angustifolius L.) to create stable herbicide (Basta) resistant cultivars is presented. |
