5.4.3
EXPRESSION OF OXALATE OXIDASE IN SUNFLOWER TO COMBAT SCLEROTINIA DISEASE

G LU, C SCELONGE, L WANG, L NORIAN, M MANCL, N YALPANI, T VORTHERMS, Z BAO, A SHAO, J HELLER, J ROUSE, E KULISEK, H SCHMIDT, L TAGLIANI and D BIDNEY

Trait and Technology Development, Pioneer Hi-Bred International Inc., Johnston, IA 50131, USA

Background and objectives
Resistance to the fungal pathogen Sclerotinia is a trait of major importance for crops such as sunflower, canola, and soybean. Sunflower Sclerotinia disease can be established at various developmental stages, with the main targets being head, stem and root tissues [1]. This suggests that resistance genes need to be constitutively expressed in multiple tissues. The major toxic and pathogenic factor produced by Sclerotinia is oxalic acid that can be converted into H2O2 and CO2 by oxalate oxidase.

Results and conclusions
A candidate gene for detoxifying oxalate is the wheat oxalate oxidase which has been used to transform a sunflower inbred line. Our greenhouse and field trials demonstrated that expression of this oxalate oxidase by constitutive promoters significantly enhances resistance to Sclerotinia in sunflower.

References
1. Gulya T, Rashid KY, Masirevic SN, 1997. In Schneiter AA, ed., Sunflower Technology and Production. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, Madison, Wisconsin, USA, pp. 263-380.