Fusarium oxysporum f. sp. dianthi transformed with marker genes as a tool for studying resistance in Dianthus

A F. oxysporum f. sp. dianthi strain, transformed with genes coding for fluorescent proteins (GFP or DsRedFP) as markers, was used to study the first host/pathogen interaction on carnation roots. The transformants’ mycelium observed under fluorescent light displayed a high expression of GFP and DsRedFP as a bright green or red cytoplasmic fluorescence. The root apparatus of a partially resistant cultivar of carnation was artificially inoculated by stable transformants and local colonization of plant tissues was monitored by means of fluorescence microscopy. A GFP transformed strain of F. oxysporum f. sp. dianthi allowed to follow first colonization steps on and within host root tissues. Implication of this research in studying resistance processes in carnation is discussed.