Cytological studies of early stages of powdery mildew in barley and wheat. VI. Antagonistic effects of calcium and lithium on the infection of coleoptiles of barley by Erysiphe graminis hordei

Earlier researchers have shown that the susceptibility of barley to infection by Erysiphe graminis hordei is enhanced by calcium ions but inhibited by lithium. Some effects of these ions on the infection process of E. graminis hordei in coleoptiles of barley were investigated in this study. Whereas 1 mM lithium chloride inhibited appressorial formation considerably and haustorial formation completely, these effects were totally offset by 10 mM calcium chloride. Moreover, whereas 5 and 10 mM lithium chloride inhibited both appressorial and haustorial formation completely, the former was offset considerably by 10 mM calcium chloride, but the latter was not.Sequential calcium chloride − lithium chloride or lithium chloride − calcium chloride treatments carried out at different times and for various durations showed that events occurring in coleoptiles 11 to 13 h after inoculation were most vulnerable to the treatments. These events correspond to infection stages involving the development of cytoplasmic aggregates, papillae, and haustoria. The data suggest that the two ions in question might compete for a common binding site in a reaction(s) associated with certain stages of appressorial and haustorial development.