The Induced Resistance Response of Carrot Root Slices to Heat-killed Conidia and Cell-free Germination Fluid of Botrytis cinerea Pers. ex Pers. 1. The Possible Role of Cell Death

The ability of a cell-free secretion from germinating conidia(germination fluid) and heat-killed conidia of Botrytis cinereaPers. ex Pers. to induce resistance in exposed carrot root tissueswas unaffected during freezing to –25 °C and rapidthawing, and by heating to 50 °C for 10 min. Activity waslost by boiling for 10 min or at room temperature after 24 h. There was less cell death (Evans blue and neutral red staining)in the surface tissue of slices pretreated with heat-killedconidia and subsequently exposed to infection than in similartissue of untreated, inoculated slices. Both inducing preparationsalone caused maceration and cell death in one or two cell layersof the slice surface. Healthy tissue killed by freezing to –25°Cfor 2 h and rapid thawing, released a factor which, when similarlytested on slices, resulted in germ-tube inhibition and reducedvisual symptoms following inoculation with live spores. Thepossibility that cell death triggered the release of a hostelicitor which caused enhanced accumulation of phytoalexinsand suberin deposition is discussed. Botrytis cinerea, carrot, induced resistance, cell death, vital staining