Qualitative Evaluation of Peach and Nectarine Saplings Using Morphological Traits

Applying the Dickson quality index (DQI) is an efficient but destructive and time-consuming method for predicting sapling quality in nurseries.Fast and low-cost prediction of the quality, establishment, and growing strength of fruit tree saplings in the orchard through the identification of morphological characteristics, which are so highly correlated with this index, is necessary for different stages of sapling production.To evaluate the relationship between the morphological characteristics in peach and nectarine saplings, bare-root saplings of 16 commercial cultivars with three replicates from 10 nurseries, located in four provinces, were studied. The samples provided from two types of non-certified sapling, grafted on the seedling rootstocks, and certified sapling on the vegetative rootstocks during the transplanting seasons of 2020-2021. Sapling height, diameter above grafting line (DAGL), root length, number of roots and branches, shoot and root fresh and dry weights, height to diameter ratio, and DQI were evaluated, and simple correlations between them were estimated. The correlation coefficients were broken down into direct and indirect effects through path analysis, with DQI as the dependent variable.The results showed that the average DQI for non-certified saplings, produced in different climates, was 14. The higher values were observed in areas with more than 3100 AGDD. In certified saplings, DQI reached to 47. Based on the results of the path analysis for DQI evaluation, the highest direct effect was related to the DAGL.DAGL is the most efficient index in the quality assessment of the saplings, due to having the highest correlation with the DQI and most of the morphological traits.