Transgenic wheat plants: a powerful breeding source

Plant breeders are always interested in new genetic resources. In thepast, the sources have been limited to existing germplasm. Geneticengineering now provides the opportunity for almost unlimited strategies tocreate novel resources. As a first stage, the Applied Biotechnology Center(ABC) at CIMMYT developed a method for the mass production of fertiletransgenic wheat (Triticum aestivum L.) that yields plants ready fortransfer to soil in 13–14 weeks after the initiation of cultures, and, over thecourse 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 ofinterest with co-transformation efficiencies around 25–30%. The reliabilityof this method opens the possibility for the routine introduction of novelgenes that may induce resistance to diseases and abiotic stresses, allow themodification of dough quality, and increase the levels of micronutrientssuch as iron, zinc, and vitamins. The first group of genes being evaluatedby the ABC are the pathogenesis related (PR) proteins, such as thethaumatin-like protein (TLP) from barley, chitinase, and 1–3-glucanase. Stable integration of the genes in the genome andinheritance in the progeny were determined by phenotypical analyses thatchallenged the plants against a wide range of pathogens. Using these genes,we have recovered more than 1200 independent events (confirmed byPCR and Southern blot analyses) that show responses to the pathogens thatrange from tolerance to hypersensitive reactions. The quantity andanti-fungal activity of the endogenous thaumatin-like proteins were analyzedin T₁ and T₂ progeny plants. Western blot analyses showeddifferent protein patterns of the wheat endogenous TLPs. Preliminary resultsindicated that some patterns increased the resistance of transgenic wheatplants to Alternaria triticina. This relationship is being furtherinvestigated.