Development of Erysiphe pisi (Powdery Mildew) on Normal and Albino Mutants of Pea (Pisum sativum L.)

Early development of Erysiphe pisi (powdery mildew) was studied on normal peas (with chlorophyll), natural albino mutants (without chlorophyll) and on chimeric leaves of pea induced by ethyl methane sulphonate (EMS) under di€erent light exposures. Di€erent light regimes [continuous light; continuous darkness; short day (8 h light/16 h darkness); long day (16 h light/8 h darkness)] did not in¯uence the early development of E. pisi on pea leaves. However, under continuous dark- ness a lower number of haustoria was observed in com- parison with other treatments. Erysiphe pisi failed to develop on naturally developed complete albino leaves as well as on the albino parts of chimeric leaves induced by EMS treatment. A lesser number of appres- soria and haustoria was observed on albino leaves. Results suggest that the presence of some nondi€usable chemical(s) in normal leaves of pea is essential for the establishment of successful biotrophy.