Correlation Between Morphological Traits and Vigor in Plum Seedlings

Indicators for predicting the quality and vigor of fruit tree seedlings can be worthwhile if they are conveniently and visually assessable in various climatic regions. Since allometric relationships exist between plum seedling vigor index and morphological traits, this study evaluated morphological features in plum seedlings while determining their quality and vigor. The samples were of major commercial varieties from several regions of Iran, and the assessments followed path analysis and multiple linear regression. Plum seedlings of 8 commercial cultivars were harvested in three replicates from 11 nurseries in four provinces. Morphological indicators included seedling height, diameter above the graft line (DAGL) and at root-collar (RCD), root length, number of roots and branches, seedling vigor, dry weights of aerial parts and roots (ADW and RDW, respectively), and ratio of height to DAGL and seedling height to ADW. Simple correlations among these variables appeared diverse, and the correlation coefficients broke down into direct and indirect effects through path analysis, with vigor as the dependent variable. This variable increased with some of its components, including DAGL and dry weight. However, the ratio of height to DAGL decreased when the accumulated growing degree-days (AGDD) increased from 2700 to about 4500 °C per day in the various regions. Average vigor values of certified and uncertified seedlings were 11.7 and 19.2, respectively. Among the visually assessable traits in the nursery, DAGL showed a higher correlation with the vigor variable and other morphological features, thus making it the most important index for plum seedling evaluation.