Peach trees, cv. ‘Sanyo Suimitsuto’, were trained to a central leader system using two species of rootstock,
Pruns tomentosa Thunb. and
P. persica Batsch. Growth of shoot, root and fruit were measured 6 and 8 years after the trees had been planted, when they were considered to be adult.
1. A tree on
P. tomentosa produced a higher percentage of spurs (shoots shorter than 10cm) than a tree on
P. persica. Such spurs completed elongation by the middle of May and produced more leaves per unit length than longer shoots. Shoots of the tree on
P. persica continued to elongate until the middle of June, and were frequently longer than 20cm.
2. Newly growing white roots of
P. tomentosa rootstock increased rapidly in late April and early May. Most of the white roots then disappeared in the middle of June as a result of suberization. The start of new root growth of
P.
persica rootstock was slower by one month than that of
P. tomentosa, and a large number of white roots of
P. persica rootstock were observed until the middle of July.
3. Fruits of the tree on
P. tomentosa grew actively even during the period of stone hardening. They reached full ripeness 4 or 5 days earlier and were larger than those on
P. persica. In 1983, the content of soluble solids in the former was higher than that in the latter, but the relationship was reversed in 1985 because of heavy rainfall and poor sunshine during late June and early July, shortly before the harvesting of the fruits on
P. tomentosa.
4. From these results, we conclude that
P. tomentosa is a preferable rootstock for training peach trees to a central leader system, particularly when considering fruit growth. Trees on
P. persica, however, can also be successfully trained to this system by allowing the tree to bear many fruits at a younger age and by practising proper summer pruning.
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