Transgenic Wheat Plants: A Powerful Breeding Source

Abstract

Plant breeders are always interested in new genetic resources. In the past, the sources have been limited to existing germplasm. Genetic engineering now provides the opportunity for almost unlimited strategies to create novel resources. As a first stage, the Applied Biotechnology Center (ABC) at CIMMYT developed a method for the mass production of fertile transgenic wheat (Triticum aestivum L.) that yields plants ready for transfer to soil in 13–14 weeks after the initiation of cultures, and, over the course of a year, an average production of 5–6 transgenic plants per day. CIMMYT elite cultivars are co-bombarded with marker gene and a gene of interest with co-transformation efficiencies around 25–30%. The reliability of this method opens the possibility for the routine introduction of novel genes that may induce resistance to diseases and abiotic stresses, allow the modification of dough quality, and increase the levels of micronutrients such as iron, zinc, and vitamins. The first group of genes being evaluated by the ABC are the pathogenesis related (PR) proteins, such as the thaumatin-like protein (TLP) from barley, chitinase, and 1–3 ß-glucanase. Stable integration of the genes in the genome and inheritance in the progeny were determined by phenotypical analyses that challenged the plants against a wide range of pathogens. Using these genes, we have recovered more than 1,200 independent events (confirmed by PCR and Southern blot analyses) that show responses to the pathogens that range from tolerance to hypersensitive reactions. The quantity and anti-fungal activity of the endogenous thaumatin-like proteins were analyzed in T₁ and T₂ progeny plants. Western blot analyses showed different protein patterns of the wheat endogenous TLPs. Preliminary results indicated that some patterns increased the resistance of transgenic wheat plants to Alternaria triticina. This relationship is being further investigated.