Powdery mildew (Blumeria graminis f. sp. tritici) infection and amount of key defence chemicals - cyclic hydroxamic acids - of field cultivated wheat (Triticum aestivum L.)

Abstract

Cultivated wheat varieties have different degrees of resistance against powdery mildew. Cyclic hydroxamic acids are key defence chemicals of wheat. Examinations comprised the measurement of cyclic hydroxamic acid content and powdery mildew infection of three varieties (Lukullus, Lennox, Ispan) and a hybrid (Hystar) of field cultivated wheat, and the effectivity of two biological (Polyversum and Trifender) and one conventional fungicide (Solyom) on powdery mildew. Sample collection and measurement of fungus infection were carried out on three occasions: at BBCH 23-24, BBCH 32-33 and BBCH 77-83 phenological phases. Variety/hybrid and sampling time has significant effect on cyclic hydroxamic acid content, but there was no direct correlation between hydroxamic acid content and powdery mildew infection. Differences were found amongst varieties/hybrid in powdery mildew infection too. Only the hybrid, Hystar, showed considerable infection at every sampling time. The conventional chemical out of fungicides alone proved to be effective, and its effectivity lasted for five weeks.