Clonal propagation of a selected historical gene pool of evergreen azaleas

Many exotic plants were introduced in Italy during the 19th century. Particularly, a significant gene pool of evergreen azaleas was set up in public and private gardens. To conserve and exploit these genetic resources, the present study investigated the responses of 104 genotypes (50 Japonica, 50 Indica and 4 Amoena type) to clonal multiplication. Growth aptitude, height/diameter ratio (H/D), roundness index, number of branches per plant, and branch length were analyzed. Vegetative propagation allowed to obtain numerous plants (54 plants/genotype) with uniform characteristics. Elevated variability in growth responses between genotypes within group was shown, even if differences between local horticultural groups were found. Amoena genotypes showed the highest number of branches (10.9), and the lowest roundness index (0.96), opposite to Indica genotypes (number of branches = 6.29; roundness index = 1.03). Both groups resulted higher (Indica 33.7 cm and Amoena 34.4 cm) than Japonica (32.2 cm). The Principal Component Analysis distributed specimens without a precise clustering. In general, genotypes were mainly separated by the HD ratio (eigen vectors= -0.220) and the branch length factors (eigen vectors= 0.198). The wide variability observed in this historical gene pool suggests the possibility to find genetic resources with interesting traits to be used in future breeding programs, for improving morphological characteristics or abiotic stress tolerance.