Performance of apricot cultivars ‘Harcot’ and ‘Goldrich’ on different rootstocks in young orchard when using various grafting heights

Two apricot cultivars, 'Harcot' and 'Goldrich', were grafted onto rootstocks 'Adesoto (R)', 'Kuban 86', 'Myrobalan 29C' ('M29C'), 'MY-KL-A', 'St. Julien A' (standard), and 'Wavit'. Their performance was evaluated in the years 2017-2020. All the rootstocks were grafted 10 cm above the ground. In addition, both scion cultivars were grafted on 'M29C' and 'St. Julien A' at 60 cm height. The goal was to test their performance, including tree mortality. The trees were planted in the experimental orchard of the Research and Breeding Institute of Pomology Holovousy in the Czech Republic in autumn 2014. The cumulative yield, average fruit weight, trunk cross-sectional area (TCSA), crown volume, yield efficiency related to TCSA and to crown volume, suckering, mortality, and tree positivity to European stone fruit yellows phytoplasma (Candidatus Phytoplasma prunorum; ESFY) were assessed. For cultivar 'Harcot', the trees on 'M29C' were the most productive with similar yields but higher vigour and crown volume in comparison with 'St. Julien A'. For cultivar 'Goldrich', similar results were found. The suckering of rootstocks was negligible in all combinations. For both cultivars, interesting results were found, with 'Wavit' giving the trees low vigour, small but very productive crown, and good fruit weight. Mortality in the first years was very low, but the main problem of plantation was the infestation by ESFY. 'Harcot' trees were more infested by ESFY than 'Goldrich' trees. Grafting in a higher position did not provide any practically significant benefits. ESFY infestation and scion cultivar sensitivity appeared to be much more important factors of tree decline than the effect of rootstock in marginal growing conditions.