Over a period of seven years (2009-2016) hydroponic chyrsanthemum cultivation has been developed and<br/>tested in practice. Where the system delivered up to 25% higher yields at smaller scale, the larger systems of<br/>250-300 m2 turned out very sensitive to root infection. Research then focussed to understanding the key factors<br/>that caused the plants to become sensitive. However, where the larger system showed much disease incidence<br/>every summer for three years in a row, at smaller scale the symptoms could not be induced despite application<br/>of extreme cultivation measures.<br/>The studies were the first to apply next generation sequencing to microbial populations in cultivation systems.<br/>The results gave evidence for shifting population dynamics due to inoculation and water temperature. Also the<br/>inoculation with beneficial microbes was found to have a positive effect on recovery of the roots upon infection.<br/>This effect, however, was only found in the research-facility. At larger scale potential beneficial effect could not<br/>prevent significant yield loss.