Effet de L'acide Caféoylshikimique des Racines du Palmier Dattier sur L'activité et la Production des Enzymes Hydrolytiques de Fusarium oxysporum f. sp. albedinis

Effect of caffeoylshikimic acid of date palm roots on activity and production of Fusarium oxysporum f. sp. albedinis cell wall‐degrading enzymes The caffeoylshikimic acid (CSA), a major phenolic compound of date palm roots, represents one of the resistance factors of the host to Fusarium oxysporum f. sp. albedinis. The CSA was tested at various concentrations (0,25 to 3 µ mol/ml) on the activity and the production of F. oxysporum f. sp. albediniscell wall‐degrading enzymes (CWDE): proteases, cellulases, pectinemethyl‐esterases (PME), polygalacturonases (PG) and polygalacturonate trans‐eliminases (PGTE). The results obtained show that CSA had very little effect on the activity of the various enzymes although it greatly reduced their production. The mycelial growth was also affected by CSA, but this does not explain why only the production of CWDE was noticeably reduced. In order to explain this differential effect of CSA on the activity and production of CWDE, in one group of experiments the effects of the products of hydrolysis of CSA (caffeic acid and shikimic acid) was tested and in another, the effect of the products of CSA (quinones) obtained by tyrosinase oxidation was investigated. The results obtained show that the shikimic acid did not have a significant effect on the activity of the CWDE but presented a weak inhibition of their production.The caffeic acid showed a larger inhibition of the activity of the various CWDE that was more than that of CSA and its inhibiting effect appeared to be more important during their production. The oxidation of CSA by tyrosinase was accompanied by a greater inhibition of the activity of the various CWDE. This inhibition was appreciable in comparison with that observed due to the effect of non‐oxidized CSA on CWDE production. In the same way, oxidation of caffeic acid provoked a greater inhibiting effect on the activity of CWDE than unoxidized caffeic acid. These results suggests that CSA generates products of hydrolysis (in particular caffeic acid) and products of oxidation (quinones) which inhibit the activity of the proteolytic, cellulolytic and pectinolytic enzymes produced by F. oxysporum f. sp. albedinis in the culture medium.     

Identification des acides caféoylshikimiques des racines du palmier dattier, principaux composés fongitoxiques vis-à-vis de Fusarium oxysporum f. sp. albedinis

5-caffeoylshikimic acid and its isomeres of position (dactylifric acid) found in the roots of date-palms ( Phoenix daetylijera L.) inhibit the germination of conidia and the growth of the mycelium of Fusarium oxysporum f. sp. albedinis . The acid content accumulated in resistant cultivars are toxic to fungi, whereas that accumulated in sensitive cultivars does not seem to affect growth and development of the parasite. This well demonstrates the implication of caffeoylshikimic acid in the resistance of the date-palm to this fusarium disease. Moreover, these results will be of great use, especially for screening resistant genotypes obtained from directed crossings or from in vitro cultures.     

The Palmier date palm and Fusarium infection. II. Report on the stereochemistry of monosaccharides and their various derivatives and the growth of Fusarium oxysporum f.sp. albedinis (Killian et Maire) Gordon]

Fusarium oxysporum albedinis was grown in the presence of 20 different sugars or their derivatives. The results obtained were correlated with the stereochemical structure of the main oses. Osmotic phenomena as well as active and selective transport were used to explain differences in utilization of oses of very near structure. Based on the affinity of the fungus for mannose, a hypothesis is formulated concerning the fungus action in the host.     

Characterization of Isolates of Fusarium oxysporum Schlecht. f. sp. vasinfectum (Atk.) Snyd. & Hans., Races 1-6, by Cellular Fatty Acid Analysis

Fatty acid analysis, a common method for the identification of bacteria, was modified and applied to characterize isolates of Fusarium oxysporum f. sp. vasinfectum. After evaluating the fatty acid profiles by means of cluster analysis and three-dimensional plotting of the main fatty acids, the isolates were classified into five groups. Identical patterns were obtained for isolates of races 3 and 5 and for isolates of races 2 and 6. Isolates with so far unknown race determinations were arranged into their corresponding fatty acid groups.     

Fuciniceras paradoxus nov. sp. (Harpoceratinae, Ammonitina) du Domérien portugais. Réflexion sur le sens taxonomique d’un assemblage paradoxal de caractères

A new ammonite (Fuciniceras paradoxus) is described here. This Lower Domerian species is based on a recently revised collections which came from the Maria Pares section (Rabaçal area, South of Coimbra, Portugal). Curiously, shell of F. paradoxus bears both diagnostic traits for the genus Protogrammoceras SPATH (e.g. acute ogival ventral area) and Fuciniceras HAAS (e.g. angulirursiradiate rib). Thus, the new species can be viewed as a morphological puzzle and as a challenge for taxonomists. The amazing collection of morphological traits previously suspected as highly improbable because of biomechanical constraints (1) confirms the inadequacy of the traditional use of the genera Protogrammoceras and Fuciniceras, (2) refutes the idea of a univocal biomechanic link between the ventral area morphology and the ventral segment of ribs. If this analysis mainly concern the Harpoceratinae subfamily, its generalisation can also be interesting for other ammonites or molluscan groups.