High resistance to Sclerotinia sclerotiorum in transgenic soybean plants transformed to express an oxalate decarboxylase gene

Pathogenesis of Sclerotinia sclerotiorum (white mould) has been associated with fungal secretion of oxalic acid (OA). Enzymes capable of degrading OA have been utilized to produce transgenic resistant plants. Transgenic soybean lines containing the decarboxylase gene (oxdc) isolated from a Flammulina sp. were produced by the biolistic process. Molecular analysis revealed successful incorporation of the gene into the plant genome and showed that the oxdc gene was transferred to the progeny plants. Sixteen T-2 transgenic events were screened for S. sclerotiorum resistance using a detached leaf assay. The white mould disease progress curve displayed a significant delay in symptom development in all oxdc events compared with the nontransgenic genotype. Area under the disease progress curve (AUDPC) showed reduction in severity ranging from 61% to 96% comparing the oxdc events with the nontransgenic control. One event (OXDC.9.21) presented some plants that did not show any symptoms after 92 h. RT-PCR analysis for detection of oxdc gene transcripts suggested that expression of the oxdc gene is associated with resistance to S. sclerotiorum.