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 β-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 1200 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 antifungal activity of the endogenous thaumatin-like proteins were analyzed in T 1 and T 2 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.

Genetic basis of yield as viewed from a crop physiologist's perspective

“…Romagosa et al (1996) found different QTL × E of adapted cultivars of some major crops (e.g. Koebner & Snape, 1999;Pellegrineschi et al, 2001;Horvath et al, 2002). The usefulness of these advancements, in the case of traits controlled by major genes or few genes, is evidenced by the number of transgenic crops grown in many regions.…”

Identification of Alternaria spp. on wheat by pathogenicity assays and sequencing

“…Bansi, an old Indian durum wheat cultivar, was reported as susceptible to A. triticina in the 1960s (Prabhu & Prasada, 1966). Wheat genotypes RR21 and Bobwhite SH9846, reported previously as susceptible (Sinha et al ., 1991; Chaurasia et al ., 1999, 2000; Pellegrineschi et al ., 2001), were found to be highly resistant to all A. triticina isolates used in this study. Alternaria alternata IMI 289680, MUCL 42372, MUCL 44262 and MUCL 45332, A. arborescens MUCL 42525, MUCL 44259, MUCL 44260, MUCL 44261 and MUCL 45333, and A. tenuissima MUCL 42464 and MUCL 42561 were found to be nonpathogenic on wheat, despite being collected from wheat samples showing leaf blight lesions apparently induced neither by the tan spot nor by the spot blotch pathogens, but alleged to be caused by A. triticina .…”

“…Recently, Pellegrineschi et al . (2001) suggested that resistance to alternaria leaf blight in transgenic wheat plants might be increased by the antifungal activity of thaumatin‐like proteins from barley, a nonhost of A. triticina .…”

“…b Susceptible to A. triticina (Prasada & Prabhu, 1962). c Susceptible to A. triticina (Pellegrineschi et al, 2001). d Susceptible to A. triticina (Sinha et al, 1991;Chaurasia et al, 1999Chaurasia et al, , 2000.…”

“…Recently, Pellegrineschi et al (2001) suggested that resistance to alternaria leaf blight in transgenic wheat plants might be increased by the antifungal activity of thaumatin-like proteins from barley, a nonhost of A. triticina. However, these preliminary observations should be confirmed with regard to the effect of physiological leaf spot on wheat genotype Bobwhite SH9846, since this genotype was found to be resistant to A. triticina in the present study.…”