ISHS Acta Horticulturae 554: World Congress on Soilless Culture: Agriculture in the Coming Millennium
EVOLUTION OF PYTHIUM SPP. POPULATIONS IN SOILLESS CULTURES AND THEIR CONTROL BY ACTIVE DISINFECTING METHODS |
| Authors: | P. Rey, F. Déniel, V. Vasseur, Y. Tirilly, N. Behamou |
| Keywords: | Minor pathogens, symptomless infection, root colonization, Pythium group F |
| Abstract:
Epidemiological studies were conducted to investigate the evolution of Pythium spp. populations in soilless cultures using “closed” or “open” systems for nutrient delivery. Our investigations especially highlighted two periods of Pythium colonization. Over the first one that extended from crop start to June-July, Pythium was recovered from roots at a low level, conversely to July-August and autumn months characterized by a high colonization. Extensive root infections were not correlated with severe infections, mainly because the minor pathogen, Pythium group F, represented 75% of all Pythium isolates. However, this fungus caused limited and repeated attacks which led to yield reduction. Root rot can appear when plants are grown under cultural stress. To prevent Pythium spp. introduction and spread in greenhouses, active disinfecting methods (UV radiation, heat treatment and ozonisation) were applied to the nutrient solution used. They successfully eliminated Pythium spp. hyphae (95 to 99.9%); however, re-contamination of reservoir by Pythium spp. can sometimes occur and nullify the disinfecting procedure used. The present paper stresses the fact that, in addition to nutrient solution disinfection, all the possible sources of Pythium spp. introduction have to be controlled to reduce Pythium-root induced diseases. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
