Articles
PHENOLICS IN THE INTERACTION PSEUDOMONAS SP./ DIANTHUS CARYOPHYLLUS / FUSARIUM OXYSPORUM F.SP. DIANTHI
One of the responses of carnation plants to infection with F.oxysporum f.sp. dianthi is the accumulation of a large array of phenolic phytoalexins and stress metabolites.
Localization- and time-course studies indicated that in the highly resistant cv.
Novada, between 24 and 48 h after inoculation, the phytoalexins concentrated at the site of infection are well above the minimum active dose of fungitoxicity for F. oxysporum f.sp. dianthi and, therefore, could retard fungal growth.
Such growth retardation is considered an essential factor in the polygenic resistance mechanism, which relies on a complex system of host reactions.
Bacterization with Pseudomonas sp. strain WCS417r previous to fungal infection, enhanced the level of resistance and brought about a corresponding change in the levels of phytoalexins and stress metabolites.
In vitro, in the absence of iron, Pseudomonas sp. strain WCS417r produces salicylic acid.
Salicylic acid might be (part of) a signal sensitizing the host to produce more phytoalexins.
Treatment of the host with salicylic acid, previous to infection, however, decreases both resistance and level of phytoalexins.
The variability of the level of resistance within a cultivar is discussed.