GENETIC VARIATION FOR GROWTH VARIABLES OF Eucalyptus benthamii MAIDEN & CAMBAGE AND E. smithii R. T. BAKER PROVENANCES IN SOUTHERN BRAZIL
ABSTRACT Southern Brazil encompasses areas with a subtropical climate, with significant number of frosts, which challenge or even impair growing tropical eucalypts. Eucalyptus benthamii and E. smithii rise as alternative species of subtropical origin with considerable frost-tolerance. Here we accessed the genetic variation for diameter at breast height (DBH), height (H), volume (VOL), bifurcation and straightness of four provenances of E. smithii and two of E. benthamii, cultivated in randomized block design in a farm in Rio Negrinho, Santa Catarina, southern Brazil. We found considerable genetic variability for the traits, all directly associated with the selection for wood production and quality. In general, most of the genetic variability was found within the provenances (Q d ranged from 63.6 to 73.1%), except for straightness (Q d = 13.5% and Q st = 81.9%). Although predicting genetic gains with provenance trials might have some drawbacks, the application of the REML/BLUP method was able to predict genetic gains for the growth variables DBH, H and VOL for provenances of the two species. The highest genetic gains were predicted for a provenance of E. smithii originated from Australia (13% for DBH, 5% for H and 6.1% for VOL). However, the genetic gains from a E. benthamii provenance from Santa Catarina state were not negligible (1.2% for DBH, 1.8 for H and 2.2% for VOL). Our results provide insights for further progeny trials aimed at investigating additive genetic variance and their components, which could improve the genetic control of the traits and assist breeding programs of E. smithii and E. benthamii.