Cowpeas are nutritious grains that provide the main source of protein, highly digestible energy and vitamins to some of the world's poorest people. The demand for cowpeas is high but yields remain critically low, largely because of insect pests. Cowpea germplasm contains little or no resistance to major insect pests and a gene technology approach to adding insect protection traits is now a high priority. We have adapted features of several legume and other transformation systems and reproducibly obtained transgenic cowpeas that obey Mendelian rules in transmitting the transgene to their progeny. Critical parameters in this transformation system include the choice of cotyledonary nodes from developing or mature seeds as explants and a tissue culture medium devoid of auxins in the early stages, but including the cytokinin BAP at low levels during shoot initiation and elongation. Addition of thiol-compounds during infection and co-culture with Agrobacterium and the choice of the bar gene for selection with phosphinothricin were also important. Transgenic cowpeas that transmit the transgenes to their progeny can be recovered at a rate of one fertile plant per thousand explants. These results pave the way for the introduction of new traits into cowpea and the first genes to be trialled will include those with potential to protect against insect pests.

Bruchid larvae cause major losses of grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil and the azuki bean weevil, are pests that damage stored seeds. Others, such as the pea weevil (Bruchus pisorum), attack the crop growing i n the field. We transferred the cDNA encoding the a-amylase inhibitor (a-AI) found in the seeds of the common bean (Phaseolus vulgaris) into pea (Pisum sativum) using Agrobacferium-mediated transformation. Expression was driven by the promoter of phytohemagglutinin, another bean seed protein. The a-amylase inhibitor gene was stably expressed in the transgenic pea seeds at least to the T, seed generation, and a-AI accumulated i n the seeds up to 3% of soluble protein. This level is somewhat higher than that normally found in beans, which contain 1 to 2 % a-AI. In the 1 , seed generation the development of pea weevil larvae was blocked at an early stage. Seed damage was minimal and seed yield was not significantly reduced in the transgenic plants. These results confirm the feasibility of protecting other grain legumes such as lentils, mungbean, groundnuts, and chickpeas against a variety of bruchids using the same approach. Although a-AI also inhibits human a-amylase, cooked peas should not have a negative impact on human energy metabolism.The common bean (Phaseolus vulgaris L.) contains a family of structurally related seed proteins: PHA-E and -L, arcelin, and a-AI. PHA-E and PHA-L are strong agglutinins, i.e. classical lectins that bind carbohydrate, and arcelin, which is found only in certain wild accessions of the common bean, may be a weak agglutinin (Hartweck et al., 1991). The bean a-AI has 65 to 70% amino acid sequence identity with the other three but lacks at least one of the conserved residues needed for lectin activity. Its biochemical mode of action is to form a one-to-one complex with certain amylases (for reviews, see Chrispeels and Raikhel, 1991;Rouge et al., 1993).

The postruminal supply of the sulfur-containing amino acids, methionine and cysteine, has been reported to be a major limitation to wool growth in sheep. We aim to improve the protein quality of forage for ruminants by introducing into alfalfa chimeric genes encoding a ruminally stable, sulfur amino acid-rich protein from sunflower seeds. Four gene constructs were transferred to Australian commercial cultivars of alfalfa using Agrobacterium tumefaciens-mediated transformation and selection with phosphinothricin (PPT). Modification of the sunflower seed albumin protein-coding region by addition of the coding information for an endoplasmic reticulum (ER) retention signal was found to greatly increase the level to which the sulfur amino acid-rich protein accumulated in the leaves of transgenic alfalfa plants. The Cauliflower Mosaic Virus (CaMV) 35S promoter and two light-regulated plant gene promoter regions were compared for their ability to direct high-level expression of the introduced genes in alfalfa leaves. The highest expression of sunflower seed albumin was found in transformants bearing a gene incorporating the promoter from the Arabidopsis thaliana ats1A gene, which encodes the ribulose bisphosphate carboxylase small subunit. The highest level of sunflower seed albumin found in transgenic alfalfa leaves was estimated to constitute .1% of soluble leaf protein. This level of accumulation of the foreign protein would be predicted to supply an extra 40 mg of sulfur amino acids daily to sheep fed the modified forage. Published studies in which wool growth rates were significantly increased employed supplementation of approximately 1 to 2 g of sulfur amino acids daily.