Submitted to: Abstracts of International Powdery Mildew Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/29/1999
Publication Date: N/A
Technical Abstract: The use of transformation to obtain resistance in cereals to powdery mildews is limited by the time-consuming and expensive procedures required to obtain stably transformed plants (Bushnell et al., Can. J. Pl. Pathol. 20:137-149,1998). Typically, 9-12 months are required. To assist in the selection of candidate genes for introduction into stably transformed plants, we have utilized a prescreen to evaluate efficacy of genes for anti-fungal proteins (AFPs) in a transient expression assay as described by Nelson et al. (Transgenic Research 6:233-244,1997). Genes to be tested were introduced into epidermal cells of barley coleoptiles by particle bombardment. Concomitantly with each AFP gene, the maize C1 and R genes that regulate anthocyanin synthesis were also introduced. Cells expressing the anthocyanin genes turned red within two days after bombardment. The red cells had a high probability of coexpressing a test gene. Tissues with hred cells were inoculated with conidia of Blumeria graminis f.sp.hordei at high density. One day after inoculation, tissues were examined microscopically for development of appressoria and haustoria on and in challenged red cells compared to nearby challenged non-red control cells. In trials with AFP genes, transient expression of a rice chitinase gene(RCHI)or oat genes for thaumatin-like protein (TLP-1 and TLP-4) significantly reduced infection rates as compared to controls. Furthermore, RCHI and TLP-1 each caused many appressoria to degenerate or to be abnormally shaped. In contrast, a gene for ribosome-inhibiting protein was ineffective. We conclude that the transient expression assay is potentially useful for selecting genes with efficacy against powdery mildews.