Determination of the Suitable Morphological Indices for Characterization of Quality Categories of Grafted Sour Cherry and Sweet Cherry Seedlings

Evaluation of the Dickson quality index (DQI) is an efficient but destructive and time-consuming method for prediction of the quality of different seedlings. Fast and low-cost prediction of the quality and vigor of fruit tree seedlings at harvest time using DQI which has shown to be highly correlated with morphological characteristics, is necessary. In this study, grafted sour cherry and sweet cherry bare-root seedlings of 17 commercial cultivars with three replications from 10 nurseries in four provinces in Iran were harvested during the transplanting seasons of 2020 and 2021. The seedlings were selected from two types of certified and non-certified grafted sour cherry and sweet cherry on the seedling and clonal rootstocks, respectively. Seedling height, diameter above grafting line (DAGL), root length, number of roots and branches, fresh and dry weight, height to diameter ratio, and DQI were assessed, and simple correlation coefficients between them were calculated. Path analysis method employed to estimate direct and indirect effects of variables. The results showed that the average DQI for non-certified seedlings was 15.6. The higher values of DQI were observed in areas with more than 3400 accumulated growing degree-days. For certified seedlings, DQI decreased to 12 which is likely to be the effect of using SL64 semi-dwarf rootstock. Based on the results of the path analysis for DQI, the highest direct effect was related to DAGL. DAGL was determined as the most efficient morphological characteristic for characterization of quality categories of grafted sour cherry and sweet cherry seedlings due mainly to its highest correlation with the DQI and most of the other morphological characteristics.