Genetic parameters for F1 hybrids of Pinus caribaea var. hondurensis with both Pinus oocarpa and Pinus tecunumanii

Abstract

Genetic parameters were estimated from 5-year data collected in two 11 x 6 factorial matings, one between Pinus caribaea var. hondurensis Bart. and Golf. (PCH) and Pinus oocarpa Schiede (POOC) and the other between Pen and Pinus tecunumanii (Schw.) Eguiluz et Perry (PTEC), that were planted on two sites in Queensland, Australia. The data were also used to predict the general hybridizing ability (GHA) of the 11 PCH parents common to the POOC and PTEC factorials. Genetic parameter estimates obtained from an across-sites analysis were generally of similar magnitude in the two different hybrids. Unbiased heritability estimates from the across-sites analysis were usually intermediate between those obtained from the analysis of the data from the single sites, and estimates from the female (PCH) and male (POOC or PTEC) parents were often substantially different. Type B genetic correlations (r(gB)) between the same trait measured in the two tests were high (ranging from 0.76 to 0.95) for all traits except DBH of the PCH x PTEC hybrids (r(gB) = 0.36). Estimates of r(gB) for DBH from the female parents were generally higher than estimates for Pen between pairs of tests in these same locations, while estimates for DBH of the PCH x PTEC hybrids are similar to estimates for height in pairs of PTEC tests grown in different countries. The ratio of additive to dominance variance was 1.4 for diameter, but all other traits showed relatively little dominance variance. The ranking of the 11 PCH parents based on the GHA predictions was very similar in both the POOC and PTEC hybrid crosses for traits that were controlled primarily by additive variance (i.e., straightness and wind-firmness, where correlations between the two sets of breeding values exceeded 0.92); however, for diameter the correlation was low (r = 0.45) and not significant (at the p = 0.05 level). The implications of these results are discussed in relation to the genetic improvement of hybrids.