Deciphering morpho-agronomic determinants of the juvenile-mature phase change in apple progenies

Abstract

Various external and internal factors affect the transition from juvenile to mature phase in tree species as well as herbaceous annual plants. The comprehensive study of the evaluation of juvenility based upon physiological and morphological descriptors in deciduous trees is of crucial importance to provide accurate and consistent assessments regarding the duration of juvenile phase. In this sense, this study aimed at investigating the morpho-agronomic factors that affect the transition from juvenile to mature phase in two segregating apple progenies (‘Braeburn’בAmasya’ and ‘Granny Smith’בAmasya’) over the first two years of flowering. Both progenies showed similar patterns of data distribution among traits over two consecutive years. However, a notable difference between flowering and non-flowering seedlings was recorded in 2019 comparing to in 2018 for all traits, which can be attributed to either a large number of flowering individuals, tree age, climatic conditions or a combination of them. ‘Granny Smith’ as a female parent outperformed for shortening the juvenility phase. It was found that the plant height, trunk cross-sectional area, the number of lateral branches and branch cross-sectional area in flowering seedlings was significantly higher than of non-flowering seedlings, and can provide a reliable indication to identify juvenile or mature phase. Surprisingly, vigour balance did not show significant differences between flowering and non-flowering seedlings for the progenies and their mean in both two years. As expected, considerable variation was found in all the studied traits for all progenies in both years. The transition points from juvenile to mature phases occurred at about 70th to the 75th node in seedlings of ‘Braeburn’בAmasya’ and 93th to 104th node in seedlings of ‘Granny Smith’×’Amasya’ during two consecutive years.