ISHS Acta Horticulturae 705: V International Walnut Symposium
PHENOLIC CONTENT OF WALNUT FRUIT AS AFFECTED BY CULTIVAR AND DEVELOPMENTAL STAGE |
| Authors: | A. Solar, M. Colaric, M. Hudina, F. Štampar |
| Keywords: | Juglans regia L., phenolic compounds, seasonal variations, bacterial blight |
| Abstract:
Thirteen phenolic compounds of six commercial walnut cultivars were analysed in order to establish the influence of the cultivars and developmental stage on the phenol concentration and to recognize the link between the phenolic content and resistance of fruits to walnut bacterial blight (Xanthomonas campestris pv. juglandis (Pierce) Dowson). The nuts were collected on four sampling dates during the season. Both cultivars and developmental stage had statistically significant influence on the phenolic contents in nuts. The exception was catechin whose content did not depend on the cultivar. The interaction between the cultivar and developmental stage was significant for all investigated phenols, except for juglone. Early in the season there were important differences between the cultivars considering the contents of chlorogenic, gallic, vanillic, ellagic, ferulic, sinapic and protocatechuic acids. During the second, third and fourth dates their contents decreased and became more similar in all the cultivars. A different dynamics was seen in catechin whose concentration greatly decreased in the second term, and in the fourth term it reached half the concentration of the first term. The juglone concentration was significantly higher than the contents of other phenols in all cultivars. The late-leafing cultivars ‘Fernor’ and ‘Franquette’, which are less susceptible to walnut blight in the Slovenian climatic conditions, exhibited the highest content of total phenols. The medium-early-leafing cultivar ‘Hartley’, which is rather susceptible to blight, had the lowest phenolic concentration. In a very susceptible cv. ‘Šampion’ the total phenolic content as well as juglone concentration were very similar to the concentrations in more resistant cultivars. This proves that beside juglone some other phenolics may be involved into the defence mechanism against walnut bacterial blight. | |
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