Determination of graft compatibility in sweet cherry by a co-culture method

Abstract

SummaryCell suspensions of two sweet cherry cultivars (Prunus avium L.) ‘Sam’ and ‘Sweetheart’, and four cherry rootstocks: ‘Edabriz’ and ‘Weiroot 10’ (P. cerasus L.), ‘P. avium seedlings’ (Alkavo selection) and ‘Gisela 5’ (a P. cerasus P. canescens hybrid) were co-cultured for 14 d and their mass increase used to calculate an affinity index and the degree of compatibility between pairs of genotypes. Synergistic as well as antagonistic growth responses were observed among the various genotype combinations. The effect on growth was never significantly negative, or resulted in cell mortality. Co-culture of ‘P. avium seedlings’ and ‘Sweetheart’ had a significantly positive influence on the growth of ‘P. avium seedling’ cell suspensions, and co-culture with either of the sweet cherry cultivars had a very positive effect on the growth increase (GI) of ‘Edabriz’ cell suspensions. The GI of the sweet cherry cultivar ‘Sam’ was positively influenced by the presence of both ‘Weiroot 10’ and ‘Gisela 5’ in the co-culture chamber. The GI for the combination of ‘Sweetheart’ with ‘Gisela 5’ or ‘Edabriz’ was significantly lower than in the control, and none of the combinations with ‘P. avium seedlings’ or ‘Weiroot 10’ gave an increase in GI greater than controls of the scion cultivar ‘Sweetheart’ alone. The calculated degree of compatibility (DCcc) showed that the cultivar ‘Sam’ had no compatibility problems with the four rootstocks tested, whereas the combination of ‘Sweetheart’ and ‘Gisela 5’ had the lowest DCcc (= 0.80) which was concluded to be on the border between a compatible and an incompatible relationship. It was therefore concluded that a calculated value of DCcc < 0.80 would indicate an incompatible combination, and that values of DCcc > 1.00 would indicate healthy and strong combinations.Virus-induced incompatibility appeared to play a much larger role in explaining unsuccessful grafts observed in the nursery than previously assumed.