Genetic of phenolic compounds in walnut:: Qualitative and quantitative variations among cultivars

This work aimed at assessing the possibility of using phenolic compounds as genetic markers in walnut. Phenolic compounds are widely spread in plants. Very diversified, their synthesis depends on numerous enzymes involved in different metabolic pathways well-known today, Variation among individuals that can be qualitative (presence/absence of a particular compound) or quantitative is controlled by genetic and environmental factors. Fifteen Juglans regia cultivars and 1 Juglans nigra genotype were characterised using 9 distinct phenolic compounds extracted from young leaves and analysed by high performance liquid chromatography, Huge variation among Juglans regia cultivars was found to be very large. Both collecting date and genotype had a significant effect on the quantitative variation. One compound was specific to the variety 'Lara'. For the other compounds, variation was analysed both at qualitative and quantitative levels. Myricitrin content was higher in Juglans nigra and interspecific hybrids (Juglans nigra x Juglans regia) than in Juglans regia (cultivars and intraspecific hybrids) suggesting a strong genetic control (type of dominance) of this character. Cluster analysis was performed.