Rooting responses to wounding winter cuttings of M.26 apple rootstock

Summary

Wounding the bases of M.26 winter cuttings, especially by splitting, increased the numbers of cuttings that rooted and the numbers of roots for each cutting that rooted. The response was greatest in situations where rooting was relatively poor normally, such as in non-basal internodal tissue compared with basal cuttings, and in cuttings from hedges compared with those from stoolbeds. A significant wounding response occurred only in the presence of IBA, both when wounding preceded and followed IBA treatment. The response to wounding in the presence of IBA included the stimulation of nodular callus from the region of the inner cortex and cambium which was exposed by splitting, and from which four ranks of roots were sometimes produced. Split cuttings often survived better than normal ones under conditions when over-wet compost favoured rotting at the cutting base, because basal necrosis was confined to the proximal part of the stem where rooting occurs in normal cuttings whereas split cuttings callused and rooted at a higher position. Splitting was also associated with improved rooting at a high water suction in the çompost, possibly by enhancing water uptake.