Germination Development of Powdery Mildew on Natural and Artificial Wheat Leaf Surfaces: A Study to Investigate Plant...

Wax chemistry, especially long-chain aldehydes, and surface wettability are discussed to have a stimulating effect on the development of Blumeria graminis, the pathogen of powdery mildew on wheat. Here, these specific surface properties are investigated on leaves of different wheat varieties and on developed test systems coated with plant wax and wax components. So far, the wettability of leaves has not been achieved by artificial substrates used in in vitro studies. With the test systems developed here, a wettability comparable to that on leaf surfaces and the signal character of wax chemistry could be investigated individually and in combination. The results show that wax morphology and chemistry (analyzed by scanning electron microscopy and gas chromatography) as well as wettability of leaves have no differences that would suggest a relationship with variety susceptibility. Furthermore, the influence of wax chemistry and wettability on the process of prepenetration of B. graminis on leaves and test systems is investigated. Germination and differentiation are not stimulated on any of the test systems compared to surfaces without the signals offered. Wettability, wax chemistry, and components such as long-chain aldehydes could not be identified as decisive signals for the germination development of B. graminis.