Cultures were placed in Sunbags (Sigma-Aldrich, Munich, Germany) to prevent crosscontamination. They were raised in the greenhouse, in 18 cm diameter pots filled with an autoclaved substrate consisting of four parts (volume) gravel sand (Kieswerk Klardorf GmbH & Co Produktions KG, Schwandorf, Germany) and one part calcined attapulgite clay (Oil Dri US-Special, Typ III R; from EugenTrost GmbH & Co KG Puchheim, Germany).