NEW ZEALAND'S LONG INTERNODE BREED OF PINUS RADIATA

Pinus radiata D.Don shows marked variation in the number of branch clusters formed annually, with a corresponding variation in"internode " length (distance between branch clusters). Long internodes are commercially valuable due to greater yield of knot-free lumber in the unpruned part of the stem. Internode length is under strong genetic control and is highly amenable to selection. In a recent sawing study trees of clones selected for long internodes gave much higher lumber value as U.S. shop grades than short-internode trees. Breeding for internode length began in 1970 with the selection of 104 long-internode plus-trees. Subsequent work included open-pollinated progeny testing of both the first-generation selections and 74 second-generation selections, making and testing 153 crosses involving first- and second-generation selections, and further first-generation selections in 1985. Advanced-generation selections will be made in the control-pollinated trials in 1998. Gains in internode length entail somewhat reduced gains in volume growth, branch size, and stem quality. The Long Internode breed has been separated from the main breeding population. The goal is a tree with one or two branch clusters per year, to be grown on appropriate sites with suitable silviculture. Deployment of improved stock is by using seedlings or cuttings from control-pollinated seed. A clonal forestry option also exists. The next step to advance the Long Internode breed is likely to be forming two small elite sublines. Future breeding will largely be within the two elite sublines, allowing for unrelated crosses between sublines for production purposes