Cambial Peroxidase Enzymes Related to Graft Incompatibility in Red Maple

Abstract

Abstract Two major anodal peroxidase isozyme bands occurred with high frequency (70–80%) in the cambial tissue of red maple (Acer rubrum L.) stems and roots. Some red maples, and all silver maples (A. saccarinum L.) tested lacked the lower enzyme band. The presence or absence of the lower enzyme band was not related to the geographic origin of the plants. Because of varying degrees of polyploidy in red maples and hybrids between red and silver maples, the staining intensity of the enzyme bands, especially the lower band, varied considerably. Still, bark-ring grafts between 2-banded and 1-banded red maples exhibited incompatibility symptoms similar to other tree combinations with dissimilar cambial peroxidase isozymes. During the extended time period of 3 to 5 years required for complete envelopment of the severed stock stub in budded red maples, zones of poorly lignified cells are formed at the boundary between incompatible stock and scion cambia. After the increased growth of the scion has developed a large crown, various stresses such as wind and freezing temperatures may combine to fracture the graft union along the zone of unlignified cells. Isozyme patterns are given for many red maple cultivars, and most have both A and B bands; some data are provided on isozyme inheritance. Nurserymen may significantly reduce problems of graft compatibility in these cultivars by collecting seed for seedling rootstock production only from parent trees with AB enzyme phenotypes or, for any cultivar, by creating seed orchards that will provide seedlings of the desired enzyme properties.