Assessment of diversity in Gami Almasi apple rootstock (Malus × domestica cv. Gami Almasi) progenies by morphological attributes

Background and objectives:
The use of local dwarf rootstocks is important due to adaptation with region climate, and prevents entrance of the pests and diseases into the country and economizes procurement and production costs. Hence, in most of the countries, various apple rootstocks have been improved and introduced based on the demand of apple producers and climate conditions. Gami Almasi apple is native of West Azerbaijan province of Iran and adapted to the climatic and soil conditions of that area and has desired traits such as precocious, good compatibility with apple commercial varieties, cold and calcareous soils tolerant and easy reproduction. But due to some of the unpleasant traits; this Apple cultivar cannot be used as a rootstock. Therefore, to identify Suitable rootstocks for apple, the progenies resulting from hybridization of Gami Almasi apple were evaluated for some morphological traits in this investigation.

Materials and methods:
In order to assess morphological diversity in progenies resulting from free pollination of Gami Almasi apple (59 genotypes) and controlled pollination with MM109 apple as male parent (24 genotypes), variables were included of Leaf area, chlorophyll index, internode length of shoots, tree height, annual vegetative growth, suckers production, iron chlorosis, Burr knots, angel of branches, infection with wooly apple aphids, infection with powdery mildew, infection with pear lace bug and flexibility of branches were investigated. From 89 genotypes evaluated, 24 genotypes were obtained from controlled pollination between Gami Almasi and MM109, and 59 genotypes were obtained from free pollination of Gami Almasi. For evaluation of diversity, Correlations between traits was determined, Cluster was drawn by Ward’s Method, Discriminant and Multivariate Tests were used to determine the appropriate grouping.


Results:
Based on the results of correlation analysis, a positive and significant correlation was found between vegetative traits such as height, annual vegetative growth rate, chlorophyll index, internodes length, with branch flexibility. Also, a significant positive correlation between rate of suckers production and Burrknots, and between rate of Burrknots and infection with wooly apple aphids was detected. Cluster analysis using Ward method classified the 89 genotypes into three groups. Groups included: trees with high height, tolerant to diseases and pests, the lowest Burrknots and suckers in group I; trees with medium height, sensitive to diseases and pests, the most Burr knots and suckers in group II; trees with the lowest height, iron chlorosis, Burrknots and suckers, and semi tolerant to diseases and pests in group III.

Conclusion:
Trees in group II are not suitable rootstocks for apples, because of undesirable traits such as: production of suckers, highly infected with wooly apple aphids, having Burrknots, iron chlorosis and fragile branches. If the purpose is selecting the rootstocks for resistant to pests and diseases, and needless for scaffolding, trees in group I are appropriate. If the purpose is selecting the dwarfing rootstocks with the lowest suckers and iron chlorosis, semi tolerant to wooly apple aphids, and medium flexibility of branches, trees in group III are appropriate and should be cared.