Genetic variation of in vitro rooting ability with time in Eucalyptus globulus

The genetic control of in vitro rooting success of Eucalyptus globulus was examined in two studies, one involving 496 ortets (seedlings) from 20 open pollinated families from a single race (Jeeralang) and another involving 15 5 ortets from 15 control pollinated families (half-diallel). Rooting was ex amined in several consecutive rooting tests, spanning a one year period, al lowing the importance of genetic effects, changes over time, and the intera ction between genotype and rooting tests to be determined. Significant leve ls of additive genetic variation for rooting success were detected. The nar row-sense heritability was h(2)=0.16 and 0.27, respectively with the geneti c correlations across tests extremely high (0.83 and 0.81). The levels of s pecific combining ability and ortet (within family) by test interaction wer e low (1.5% and 5% of the total variation, respectively) but significant. R ooting ability dropped markedly during the initial few months but seemed to remain stable thereafter, at levels of 15% and 40%, respectively. Parents with an intrinsic genetic superiority for rooting can be identified on the basis of a few well replicated tests. The superiority is expected t o be mostly under additive genetic control which would allow the use of bul ked family deployment strategies as well as breeding for improved rooting a bility.