Relationships of morphological traits and ripening time during juvenile phase in apple

Young progenies were appraised with relative bearing parents for values of specific morphological traits related to earliness trait in order to defeat the juvenile period in breeding program. 38 Iranian local and imported apple cultivars with different times of ripening, from very early to very late, selected as parents to produce high yielding early descendents were formerly propagated on MM111 clonal rootstocks, grown in the identical pedo-climatic conditions. So, all the parents were classified in 3 distinct classes of earliness including very early-early ripening, mid ripening and late-very late ripening. The 3-year-old True-to-Type plants of the same parents were exploited for comparative biennial studies of 10 definite vegetative traits, defined as morphological markers, with their parents to estimate probable correlations with earliness character as the target of the current apple breeding program. Stepwise regression analysis revealed leaf length as the first trait entered to the model explaining approximately 45% of variations. Maximum and minimum direct effects obtained from path analyses for ripening time were deduced 8.71 and −7.47 for leaf length and leaf width, respectively. Maximum indirect effect belonged to leaf width through leaf length (8.17). Cluster analysis according to UPGMA procedure and principal component analysis (PCA) was used for classifying cultivars and assessment of the traits. According to the results of cluster analysis, high variability among the groups of cultivar was determined by ripening time and origin or geographic distribution. As a result, the early ripening cultivars were placed in opposite side of cluster related to the late cultivars. Furthermore, four efficient factors (traits) including total leaf chlorophyll content, leaf length, leaf width and pedicle length justified 87% of existing diversity based on factor analysis.

► Existent variability in progeny families can be efficiently used for distinction of different classes of earliness of offspring. ► Morphological markers have the key role in fruit progeny screening to overcome the time consuming juvenile phase. ► Morphological traits are significantly correlated with earliness in apple offspring. ► Most of the morphological traits have relative near genetic relations.