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 ag e and source was examined in 9 month-old Pinus radiata cuttings. The cuttin gs investigated were propagated from stock-plants aged between 2 and 5 year s, and microcuttings propagated from 12 week old stock-plants. The design i ncluded 20 families, with seven clones per family and an average of seven r amets per clone. Five traits: height, root score, root-shoot ratio, root we ight 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 ta ken from 2 year old stock-plants showing superior growth for all traits. Cu ttings harvested from stock-plants raised as seedlings showed superior grow th compared to cuttings propagated from stock-plants raised as harvested se edling stock plants (seedling stock plants previously harvest ed for microc uttings) and stock-plants raised as microcuttings. Seedlings displayed supe rior growth compared to microcuttings. Heritabilities were moderate for hei ght 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 mad e using cuttings from the same stock-plant ages to ensure that family or cl onal ranking is not adversely affected.