FUNGAL POLYGALACTURONASES AS A PARAMETER FOR FUSARIUM WILT RESISTANCE IN CARNATIIONS.
Eleven carnation cultvars each with a different level of Fusarium wilt resistance were stem-inoculated with race 2 of Fusarium oxysporum f.sp. dianthi. During the experiment disease symptoms were indexed weekly up to 12 weeks after inoculation. Four weeks after inoculation PGs were extracted from stem pieces excised directly above the inoculation site. No PG activity was found in mock inoculated plants. Only samples taken from Fusarium inoculated plants contain PG activity. A cup plate assay and a spectrophotometrical assay was used to quantify the extracted PG activity. Both methods clearly indicated a significant correlation betweend PG activity (2-cyanoacetamide assay) and disease symptoms (R-0.9 < 0.001) or PG activity and percentage resistant plants (R= 0.85 = 0.001). Determination of PG activity could therefore provide a fast and reliable test method and as such be an important aid in breeding Fusarium resistant carnation cultivars.