The objective of our study was to assess the amount of within- and among-population variation of traits of adaptive significance such as juvenile height growth, stem, leaf, root, and total dry weight of sweet chestnut (Castanea sativa Mill.) and to evaluate how genetic variation is affected by different combinations of temperature and water availability. Forty-eight open-pollinated families from a stratified sample (temperature/precipitation) of 6 natural/naturalized populations from Spain, Italy, and Greece were grown for one growth period in a factorial 2 × 2 temperature -(25 and 32°C) and watering -(well watered or periodic drought) experiment in growth chambers. Strongly significant effects of the water and temperature treatments, and temperature x water interaction were found for most growth traits. Significant population effects were found for all traits studied. The significant population x temperature x watering interaction indicated presence of some specific adaptedness. The family effects were strongly significant for all traits except for the root/stem weight ratio. The heritabilities and CVA for growth traits were generally large (0.42-0.89 and 16.2-56.6% respectively). The highest estimates were obtained in the 25°C temperature and drought treatment. The variance components for the 3-way interaction were much smaller than the family variance components. Depending on the trait, 7-13 families contributed significantly to the g x e interaction with generally low estimates of the ecovalence values, A of height growth and biomass traits with diverse patterns of its change across the treatments. The large additive variance for height growth and biomass traits found within the six studied populations of Castanea sativa suggests good prospects for adaptation during the juvenile stage to future climates.
