The expression of resistance to latent stem infection by Diaporthe toxica in narrow-leafed lupin

Resistance to latent infection by Diaporthe toxica was examined in resistant acid susceptible cultivars and breeding lines of Lupinus angustifolius (narrow-leafed lupin or blue lupine). Conidial germination (91 +/- 1% at 3 days after inoculation) or penetration of the cuticle (14 +/- 1% at 3 days and 24 +/- 1% at 5 days) by D. toxica were not affected by host resistance. After 5 days, the relative size and number of subcuticular coralloid infection hyphae differed on resistant and susceptible hosts. On susceptible hosts, the majority of coralloid hyphae were large (>100 mu m long at 21 days). Resistant hosts had the same density of coralloid hyphae (approximately 300 hyphae per cm(2)), but the majority were small (