AN ADVANCED-GENERATION TREE IMPROVEMENT PLAN FOR SLASH PINE IN THE SOUTHEASTERN UNITED-STATES

The Cooperative Forest Genetics Research Program has adopted an advanc ed-generation breeding strategy designed to maximize genetic gain in t he short term and provide for continued improvement in the long term, while maintaining a broad genetic base for gene conservation. The bree ding population consists of 933 members with an effective population s ize of 625. The population is divided into 4 strata based on genetic q uality, with the top stratum functioning as an elite population. Clone s in higher strata of the breeding population will receive more emphas is for both breeding and progeny testing, while those in the bottom st ratum will serve to maintain a broad genetic base and infuse potential ly valuable genes into upper stratum. Superimposed on the quality stra tification is a division into 2 superlines, with each superline compos ed of 12 breeding groups (for a total of 24). These sub-divisions of t he population will allow long-term breeding, while indefinitely mainta ining the ability to create production populations of outcrossed proge ny through directed controlled pollination or wind-pollinated seed orc hards. A complementary mating design will be used, with polymix progen y tests io assess breeding values, and unreplicated full-sib plots use d for within-family selection. The plan cells for a reduction lin per cooperating member workload from 60 replicated tests on 98 ha for the first generation, to 2.5 tests on 9 ha for the advanced generation.