Genetic parameters in subtropical pine F-1 hybrids: heritabilities, between-trait correlations and genotype-by-environment interactions

摘要

Growth and stem straightness traits of 29 Pinus caribaea var. hondurensis x Pinus tecunumanii (PCH x PTEC) and 26 P. caribaea var. hondurensisxPinus oocarpa (PCH x POOC) hybrid pair-crosses plus a total of 16 intraspecific families were assessed at ages 5, 8 and 15 years from planting at two sites. The PCH x PTEC hybrid was the most productive, yielding 37% more than a Pinus elliottii local control and was 21 % superior to either parental species in DBH growth. PCH x POOC hybrid was, on average, 16 % superior to either parental species for DBH. Narrow-sense heritability estimates were low to moderate for growth traits (average of 0.27) and stem straightness (0.16). The estimated additive genetic correlations between growth traits and ages within traits were high (>0.8) and positive, providing confidence in early selection based on diameter at breast height. The high proportion of estimated additive genetic variance compared to dominance variance in the F-1 pine hybrids suggests that breeding strategies that maximize the use of additive genetic variance may be effective. The ranking of the 11 PCH parents based on general hybridizing ability predictions (estimated breeding values as hybrids) was somewhat inconsistent between PTEC and POOC hybrid crosses for all traits (r(9 d.f.) = 0.38-0.45; p similar to 0.15-0.25). There was no evidence of practically important G x E interaction for the hybrids except for PCH x PTEC height growth. This study suggests that a single, multihybrid breeding population seems appropriate in Zimbabwe if the trial sites are representative of the planting target zone.