Lois Braun, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN
Hybrid hazelnuts (Corylus avellana x Corylus Americana) are a potential new woody perennial crop for the Upper Midwest being developed for their ecological and economic value. Lack of economically viable propagation methods is a significant bottleneck, not only to their wide-scale adoption but also to obtaining genetically uniform plant material for well-replicated germplasm and agronomic trials. Layering cannot produce the large numbers of clones needed and micropropagation is still too expensive. Hardwood stem cuttings are a low-cost alternative. Using dormant crown suckers collected in the fall and inserted in a mixture of peat and perlite in humidity tents placed in a greenhouse, we found that: 1) 2,000 mg L-1 Indole-3-Butyric Acid in a 50% ethanol solution is the best concentration for rooting cuttings of a range of sizes. 2) Rooting declines with increasing basal diameter of stems, but increases with increasing length of stem. 3) It is not necessary to maintain RH near 100% as we had been doing with nearly airtight sealed humidity tents. 4) Dormant stems collected in the fall soon after leaf abscission can be rooted if placed in the humidity tents after only three weeks of chilling, or up until the middle of March. Cuttings collected before leaf abscission failed to root. In spite of the improvements identified by these trials, we still typically expect only about 35% of hardwood stem cuttings to form roots, of which we expect about 85% to survive for an overall productivity of 30%. We do not expect the method ever to be productive enough to supply large numbers of plants to growers, though it can provide enough clones to be of use in a breeding program and for agronomic trials in situations where mound layering is not feasible.