Vegetative Characteristics and Early Bearing of Some Fire Blight Tolerant European Pear Cultivars on Semi-Dwarfing Pyrodwarf® and OH × F87TM Rootstocks

The aim of this study was to investigate the growth and early bearing potential of some commercial and fire blight resistant pear cultivars on OH × F87TM rootstock and to compare this rootstock with the commercial semi-dwarf Pyrodwarf rootstock. The pear cultivars were Louise Bonne, Dargazi, Spadona as the three most popular pear cultivars in Iran, and two newly introduced cultivars, Super Elliot and Packham`s Triumph, which have been evaluated under Karaj climatic conditions for four years (2017-20). The rootstocks were micro-propagated from virus free materials and the trees were two year old nursery plants. The tallest tree height was observed in cultivars Dargazi on both OH × F87TM and Pyrodwarf rootstocks and also the highest spur density was 12 spurs per meter in three graft combinations of Louise Bonne and Packhams cultivars on OH × F87TM rootstock and Spadona on Pyrodwarf. The use of two year old trees caused early bearing of trees in the first year after planting, and flowering in the second year on OH × F87TM rootstock with about 40 blossoms per tree, while Pyrodwarf had about 37.5 blossoms per tree. The highest fruit yield research period observed in cv. Dargazi and cv. Super Elliot, however, the latter showed high susceptibility to pear psylla. On the other hand, cv. Spadona which normally has a low fruit yield on Pyrodwarf rootstock, had higher fruit yield on OH × F87TM rootstock. In general, OH × F87TM rootstock, due to lower growth and relatively higher fruit yield had high yield index per trunk cross section in grafted trees, and in addition to cv. Dargazi, Louise Bonne also had high yield index per trunk cross section on this rootstock. The results showed that OH × F87TM rootstock can be considered as suitable, and even superior to Pyrodwarf, for pear cultivars in the continuation of this research.