The present work deals with the effect of root colonization by fluorescent Pseudomonas spp.strains WCS417,WCSX.13 and WCS358 on Fusarium wilt of carnation in hydroponic systems.The population of WCS417 on roots of susceptible cultivar Lena and moderately resistant cultivar Pallas was 8.8×10²cfu/cm and 9.8×10²cfu/cm root tissue,respectively;whereas that of WCS358 was 0.9×10²cfu/cm and 0.13×10² cfu/cm root tissue,respectively,two weeks after bacterization.In aerated flasks disease index of Pallas treated withWCS417 or WCSX.13 was 0.31 and 0.19,respectively,Whereas that of non-bacterized plants was 0.58 and the population of Fusarium oxysporum f.sp.dianthi (Prill.and Del.) Snyd.and Hans.(Fod),the causal agent of Fusarium wilt on carnation,developed on roots and in stem tissue of bacterized plants was lower than that of non-bacterized plants.
In Nutrient Film Technique (NFT) system,19 weeks after innocula-tion with Fod the disease incidence of Lena was reduced with 13% by WCS417,compared with that of non-bacterized control,while this strain on Pallas postponed disease symptom for more than six weeks, whereas WCSX.13 and WCS358 reducee the disease incidence on Pallas with 10% and 7%,respectively.