A competitive ELISA for detecting resistance to latent stem infection by Diaporthe toxica in narrow-leafed lupins

Resistance to Diaporthe toxica in 12 lines of narrow-leafed lupin (Lupinus angustifolius) was assessed by a competitive enzyme-linked immunosorbent assay (ELISA). Seedlings were inoculated with the pathogen and after 21 days resistance was assessed by counting latent infection structures in epidermal tissue under the microscope. Infected stem pieces were then incubated for 6 days in moist chambers before treatment with antisera to D. toxica. There was a high correlation between the ELISA reaction and the frequency of latent infection structures on the 12 lines (r = 0.92, P< 0.001). Visual confirmation of the ELISA result was obtained by further incubating the excised stems for up to 12 days and assessing the degree of fungal development. There was a high correlation between the ELISA result after 6 days incubation and visual ratings of fungal development after 12 days incubation (r = 0.89, P