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

The genetic control of in vitrorooting 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 155 ortets from 15 control pollinated families (half-diallel). Rooting was examined in several consecutive rooting tests, spanning a one year period, allowing the importance of genetic effects, changes over time, and the interaction between genotype and rooting tests to be determined. Significant levels of additive genetic variation for rooting success were detected. The narrow-sense heritability was h2=0.16 and 0.27, respectively with the genetic correlations across tests extremely high (0.83 and 0.81). The levels of specific combining ability and ortet (within family) by test interaction were low (1.5% and 5% of the total variation, respectively) but significant. Rooting 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 to be mostly under additive genetic control which would allow the use of bulked family deployment strategies as well as breeding for improved rooting ability.