Third-Cycle Breeding Strategy for Slash Pine by the Cooperative Forest Genetics Research Program

Abstract

The Cooperative Forest Genetics Research Program (CFGRP) third-cycle slash pine tree improvement program will span 11 years (2003-2013), involving a breeding population of 360 third-cycle selections and 20 full-sib (FS) progeny tests with a total of 75,000 measurement trees. Of the 360 selections, two-thirds are forward selections (selections made in 1400 second-cycle full-sib selection plots) and one-third are backward selections (excellent first- and second-cycle selections brought forward into the third cycle). Selections will be top-grafted into sexually-mature, insect-protected, seed orchard trees where third-cycle breeding can begin as soon as one year after grafting. The main breeding population is divided into ten sublines with approximately 36 selections per subline. The top 6 selections from each of the 10 sublines comprise an elite population (6 per subline x 10 sublines = 60 elite selections). The ten sublines are divided into two superlines (the orange and blue superlines). Each superline has 5 sublines containing a total 180 selections of which 30 comprise the elite population for that superline. The breeding for the main and elite populations is scheduled for three breeding seasons (2004-2006) and consists entirely of FS matings planted in replicated tests with single tree plots in incomplete block designs. For the elite population, a circular mating design will create 75 crosses in each of the 2 superlines (5 crosses for each of the 30 selections) for a total of 150 total elite FS families (75 crosses/superline x 2 superlines). Ten third-cycle elite FS progeny tests will be planted with each test having 3,000 measure trees (150 families/test x 20 blocks/test) for a total of 30,000 FS seedlings. For the main population, the circular mating design will attempt 72 crosses within each of the 10 sublines (averaging 4 crosses per selection) for a total of 720 main population crosses (72 crosses/subline x 10 sublines). Ten third-cycle main population FS progeny tests will be planted with each test containing FS progeny from half of the sublines (2 series with 5 tests for the orange subline and 5 for the blue). Assuming that only 600 of the 720 attempted FS families are successful, each test will contain 4,500 measure trees (300 families/test x 15 block/test of single tree plots) for a total of 45,000 FS progeny planted in main population tests (2 series * 5 tests/series * 4500 trees/test).