Genetic relationship between Castanea sativa Mill. trees from north-western to south Spain based on morphological traits and isoenzymes

This study is focused in the main chestnut growing areas from north- to south-western Spain. We studied 50 accessions corresponding to 22 cultivars named by local growers; 11 from Andalucia, 9 from Castilla-Leon, and 2 from Extremadura. These were compared with 22 types classified previously in Galicia (82 accessions). Ten morphological traits and five isoenzyme systems were used to classify them and establish genetic relationships. A lower genetic variability has been found in Extremadura (middle Spain) and Andalucia (south) than in Galicia (north western) which may be because of the lower importance of the crop in those areas and the geographic barriers between them. Galicia could be the origin of the types found in Castilla-Leon, Extremadura, and south-western Andalucia, and the types found in Central Andalucia were closer to those found in Castilla-Leon and Extremadura. Most accessions studied (117/132) could be classified positively, making 37 out of 44 cultivars found from northern to southern Spain. Three groups of synonymies were found in Castilla-Leon: 'Brava' and 'Negral', 'Gallego' and 'Injerto', and 'Rapega' and 'Verdello'. Most of the Spanish types have been propagated as a principal clone. Variability within the types is important and must be considered to select the best clones as cultivars.