Transgenic approaches to combat fusarium head blight in wheat and barley

Fusarium head blight (FHB) and contamination with deoxynivalenol (DON) prod uced by the primary pathogen Fusarium graminearum Schwabe [teleomorph Gibbe rella zeae (Schwein.)] have caused devastating losses to wheat (Triticum ae stivum L.), durum (Triticum turgidum L. ssp. durum Desf.Husr.), and barley (Hordeum vulgare L.) growers across the USA since the early 1990s. Evaluati on of barley, wheat, and related germplasm yielded only a few accessions wi th partial resistance. This resistance appears, in most cases, to be under polygenic control, making the development of resistant cultivars with suita ble agronomic and quality traits a challenge. The insertion of individual a ntifungal and antitoxin genes via genetic transformation has the potential to aid in development of resistant wheat and barley cultivars. Although whe at and barley transformation has been achieved in several laboratories, the development of a high throughput wheat and barley transformation systems h as been slowed by genotype effects on plant regeneration, low transformatio n efficiencies, somaclonal variation, and problems with transgene inheritan ce and stability of expression. Among the antifungal genes targeted to comb at FHB are coding sequences for proteins that degrade fungal cell walls, di sorganize fungal membranes, bolster the host defense response systems, and interfere with fungal protein synthesis, pathogenesis, and/or accumulation of DON. Promoter sequences have been selected that confer high levels of ex pression to the antifungal constructs, particularly in the spike tissues wh ich are susceptible to FHB. As more antifungal genes are inserted into whea t and barley, field and greenhouse evaluation will show whether transgenes achieve their potential in the fight against FHB.