Predicting the growth potential in some apple (Mallus domestica Borkh.) hybrid ‎rootstocks by study of vegetative characteristics

The selection of promising progenies in the early stages is one of the methods for rootstock breeding of fruit trees. In this study, vegetative traits in 11 apple genotypes with MM111 as control were investigated. The results showed that there was a significant difference between the genotypes of the studied bases in terms of vegetative traits and were classified into three general categories based on their growth potentials: 1. AR4, AR8, AR11, as dwarf genotypes with the lowestbiomass, the lowest growth rate and the highest stomatal density per leaf area unit. 2. AR1, AR3, AR6, AR7, AR9as vigorous genotypes had the highest biomass, the highest growth rate and the lowest stomatal density per leaf area. 3. AR2, AR5, AR10, MM111 had an average amount of biomass, growth rate and stomatal density per leaf area. Dwarf genotypes had the highest and vigorous genotypes had the lowest ratio of dry weight of root to shoots. Longitudinal growth of root growth in genotype of apple rootstocks had no direct relation with rootstock vigor, but there was a reverse correlation with horizontal extension. AR1, AR4, AR5, AR10 genotypes had longer roots than other genotypes of rootstocks, with lowest horizontal extension of rootsand AR2, AR3, and AR8 genotypes with highest horizontal extension hed lowest longitudinal root growth.