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S. Pereira-Lorenzo, J. Fernández-López, and J. Moreno-González

Different chestnut (Castanea sativa Mill.) cultivars are at present grown in the region of Galicia, northwestern Spain, but no distinguishing traits among cultivars have been defined so far. The objectives of this research were to 1) describe the intra and intercultivar variability of chestnut cultivars; 2) define primary morphological traits to be useful for a simple morphological classification system of the cultivars; and 3) study the association between some environmental variables and the morphological traits. Seventeen morphological traits in a sample of 373 trees belonging to 82 local cultivars of chestnut were studied by methods of numerical taxonomy, principal component and cluster analysis. These traits were selected from 135 previously studied as having possible discriminating taxonomic value. Significant variability among cultivars and among trees within cultivars was found for most of the traits. The trees were grouped according to the degree of dissimilarity on the basis of the Mahalanobis generalized distance. Most of the clones collected under a specific cultivar name were included within the same cluster group enabling us to classify 53 of the cultivars studied. A hierarchical classification system that identifies eight cultivar groups is proposed based on four discriminating levels: nut size, fruit shape, male flower type and length of burr spines. Most of the correlations between the environmental variables and the morphological traits were no significant or had a low value. The lack of correlation between the environmental variables and nut size indicates that this important trait is under strong genetic control, it is not influenced by environmental conditions and it is consistent throughout the area sampled.

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S. Pereira-Lorenzo, J. Fernández-López, and J. Moreno-González

Two-hundred and ninety-five trees sampled from seventy-five local chestnut (Castanea sativa Mill.) cultivars in northwestern Spain, which had been previously studied morphologically, were further analyzed for five isoenzyme systems, encoded by seven loci. Objectives of this study were to 1) describe the intracultivar and intercultivar variability by isoenzyme analysis and to compare it with the morphological variation and 2) establish a classification of the cultivars and to discuss its relation to the morphological classification. Variability within and among cultivars was detected, confirming the previous morphological results. The level of the observed heterozygosity in this Spanish population was higher than expected and also higher than that found in other European populations. Because of the great diversity discovered, this material seems to be worthy for introducing and maintaining in a germplasm bank. Nineteen main clusters were identified for the twenty-three most widely distributed cultivars. On the average, 61% of the trees belonging to a specific cultivar was included in the same cluster. The remaining 39% was scattered in other clusters, which indicates intracultivar variability. Therefore there is opportunity for selection within cultivars. Two clusters included three important cultivars each. This suggests possible synonymies. No correlation between morphological traits and the isoenzymic alleles was detected. The isoenzyme technique identified a higher number of cultivars increasing the information obtained with morphological traits. Correlations between the frequency of some of the alleles and the altitude and other environmental variables suggest that selection of the best adapted genotypes has occurred.