Genetic Control of Propagation Effects and the Importance of Stock Plant Age and Source on Early Growth in Cuttings of Pinus radiata

The genetic control of propagation effects and the impact of stock-plant age and source was examined in 9 month-old Pinus radiata cuttings. The cuttings investigated were propagated from stock-plants aged between 2 and 5 years, and microcuttings propagated from 12 week old stock-plants. The design included 20 families, with seven clones per family and an average of seven ramets per clone. Five traits: height, root score, root-shoot ratio, root weight and shoot weight, were measured at nine months after planting (setting). Early growth in cuttings was found to be affected by genotype and stock-plant age and an interaction between these two effects. Cutting performance was found to decline with increasing stock-plant age, with the cuttings taken from 2 year old stock-plants showing superior growth for all traits. Cuttings harvested from stockplants raised as seedlings showed superior growth compared to cuttings propagated from stock-plants raised as harvested seedling stock plants (seedling stock plants previously harvested for microcuttings) and stock-plants raised as microcuttings. Seedlings displayed superior growth compared to microcuttings. Heritabilities were moderate for height and root-shoot ratio, and low for root and shoot weight and root score. The ranking of families was found to vary with increasing stock plant age. It is recommended that selection and deployment of genetic material is made using cuttings from the same stockplant ages to ensure that family or clonal ranking is not adversely affected.