Expression of an oxalate decarboxylase gene from Flammulina sp in transgenic lettuce (Lactuca sativa) plants and resistance to Sclerotinia sclerotiorum

Sclerotinia sclerotiorum causes rot in a broad range of crops including lettuce, soybean, dry bean and tomato. Pathogenesis of Sclerotinia has been associated with the copious production of oxalic acid. Enzymes capable of degrading oxalic acid have been utilized to produce transgenic resistant plants. Transgenic lettuce lines containing the decarboxylase gene (oxdc) isolated from a Flammulina sp. were produced by Agrobacterium-mediated transformation. Out of 80 regenerated plants, PCR analysis revealed the presence of the oxdc gene in 34 lines. Except for eight lines, the primary transformants transferred the foreign gene to the first generation in a Mendelian fashion. In a detached-leaf assay inoculated with agar plugs of a 2-day-old S. sclerotiorum culture, two lines (P100 and P43) were symptomless, while line P57 showed a delay in symptom development when compared with a nontransgenic control line. RT-PCR analysis carried out with the resistant lines showed the expression of oxdc gene transcripts.