Development of Erysiphe pisi (powdery mildew) on normal and albino mutantsof pea (Pisum sativum L.)

Early development of Erysiphe pisi (powdery mildew) was studied on normal p eas (with chlorophyll), natural albino mutants (without chlorophyll) and on chimeric leaves of pea induced by ethyl methane sulphonate (EMS) under dif ferent light exposures. Different light regimes [continuous light; continuo us darkness; short day (8h light/16h darkness); long day (16h light/8h dark ness)] did not influence the early development of E. pisi on pea leaves. Ho wever, under continuous darkness a lower number of haustoria was observed i n comparison with other treatments. Erysiphe pisi failed to develop on natu rally developed complete albino leaves as well as on the albino parts of ch imeric leaves induced by EMS treatment. A lesser number of appressoria and haustoria was observed on albino leaves. Results suggest that the presence of some nondiffusable chemical(s) in normal leaves of pea is essential for the establishment of successful biotrophy.