Adventitious root formation in <i>Castanea</i> sp. semi-hard cuttings is under moderate genetic control caused mainly by non-additive genetic variance

Breeding programmes of European chestnut (Castanea sativa Mill.) for disease resistance have focused on interspecific hybridization followed by clonal propagation. Although chestnut species are recalcitrant to rooting by cuttings, it is possible to mass propagate new softwood cuttings taken from shoot stumps. To determine the importance of genetic control in adventitious root formation in chestnut, two trials were conducted with 705 ortets from 25 young full-sib families generated by combining 11 different parents including seven C. sativa, one C. crenata, one C. mollissima, and two F 1 hybrid (C. crenata × C. sativa) individuals. Rooting variables were analysed using an incomplete diallel model, and statistical analyses were performed using the MIXED and GLIMMIX procedures for continuous and binomial variables, respectively. Very high rooting percentages were obtained (91% and 82%) and the cuttings showed adequate numbers of roots (17 and 10); both characteristics were correlated ([Formula: see text] = 0.93) and presented moderate genetic control ([Formula: see text] = 0.33 for the presence of root (Proot); 0.43 and 0.35 for number of roots (Nroots)) due mainly to dominance and epistasis ([Formula: see text] = 0.21 for Proot; 0.23 and 0.27 for Nroots). There were good rooting ortets within all families, and accordingly, it is possible to select for rooting capability within each family, at least at a young age.