SUPPRESSION OF BOTH INDUCED RESISTANCE AND PHYTOALEXIN PRODUCTION BY SALICYLIC ACID DURING ELICITATION OF CARNATION CUTTINGS

Resistance of Carnation cuttings to Phytophthora parasitica Dastur can be induced by dipping the cuttings in a fungal extract.
The neoformation of two fungitoxic phenolic compounds : dianthalexine and substance 6 (phytoalexins) is always observed in these resistant elicited tissues.

The elicitor is a water suspension of mycelial walls fine powder (concentrations : 0.05 – 5 g1^-1). After a 24 h elicitation part of the cuttings is extracted for phytoalexin quantitation by High Performance Liquid Chromatography and the rest is inoculated with zoospores, then kept under mist system.
Contamination levels are recorded 6 days after inoculation : water treated control is fully susceptible, while elicited cuttings are completly resistant.

When salicylic acid (5 x 10^-5 to 2 x 10^-4M) is added to the elicitor at lower concentrations than 1 g1^-1, the neoformation of the phytoalexins is totally inhibited and the cuttings remain susceptible.
When elicitor concentration is 5 g1^-1, phytoalexin accumulate to low levels, but the cuttings are partially protected ; in that case a preliminary study shows that these cuttings highly and rapidly accumulate phytoalexins a few hours after the end of the treatment, so that the correlation between Carnation resistance to P. parasitica and the neoformation of phytoalexins is maintained.
General involvment of these phenolic compounds in Carnation resistance to diseases is discussed.

II International Symposium on Carnation Culture

M. PONCHET, V. DUPREZ, P. RICCI

https://doi.org/10.17660/ActaHortic.1983.141.9