GENETIC-PARAMETERS FOR F1 HYBRIDS OF PINUS-CARIBAEA VAR HONDURENSIS WITH BOTH PINUS-OOCARPA AND PINUS-TECUNUMANII

Genetic parameters were estimated from 5-year data collected in two 11 x 6 factorial matings, one between Pinus caribaea var. hondurensis Ba rr. & Golf. (PCH) and Pinus oocarpa Schiede (Pooc) and the other betwe en PCH and Pinus tecunumanii (Schw.) Eguiluz et Ferry (PTEC), that wer e planted on two sites in Queensland, Australia. The data were also us ed to predict the general hybridizing ability (GHA) of the 11 PCH pare nts common to the POOC and PTEC factorials. Genetic parameter estimate s obtained from an across-sites analysis were generally of similar mag nitude in the two different hybrids. Unbiased heritability estimates f rom the across-sites analysis were usually intermediate between those obtained from the analysis of the data from the single sites, and esti mates 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 Pea x PTEC hybrids (r(gB)=0. 36). Estimates of r(gB) for DBH from the female parents were generally higher than estimates for PCH between pairs of tests in these same lo cations, while estimates for DBH of the PCH x PTEC hybrids are similar to estimates for height in pairs of PTEC tests grown in different cou ntries. The ratio of additive to dominance variance was 1.4 for diamet er, but all other traits showed relatively little dominance variance. The ranking of the 11 PCH parents based on the GHA predictions was ver y similar in both the Pooc and PTEC hybrid crosses for traits that wer e controlled primarily by additive variance (i.e., straightness and wi nd-firmness, where correlations between the two sets of breeding value s exceeded 0.92); however, for diameter the correlation was low (r=0.4 5) and not significant(at the p=0.05 level). The implications of these results are discussed in relation to the genetic improvement of hybri ds.