Mass controlled pollination of Eucalyptus globulus: a practical reality

Mass production of seed by controlled crossing of selected individuals is an increasingly important method of capturing genetic gain from tree breeding. In Eucalyptus the conventional controlled pollination (CP) method requires at least three separate visits to a flower, and seed is correspondingly costly. This paper reports development of a cost-efficient pollination technique referred to as one-stop pollination (OSP) for application in seed orchards of Eucalyptus globulus Labill, in Chile. Emasculation of the flower at anthesis is followed by slicing the stigma and top of the style to provide a site for pollen adherence. Pollen is applied immediately, followed by isolation of the style from contaminating pollen by covering with a section of tubing. It is then not necessary to revisit until capsule harvest. Seed yield per capsule after OSP treatment was equivalent to that achieved by treating flowers with supplementary pollination at the time of natural stigma receptivity. Only 5% of those flowers pollinated at anthesis without style wounding set a capsule, compared with 69% with OSP. Seed yield for OSP averaged 26 seeds per capsule compared with 12 for open-pollinated samples from the same trees. The effect of orchard location on OSP harvest percentage and seed yield was demonstrated. With application of OSP in the environment of the Chilean orchard, we estimate a sevenfold reduction in seed production cost in comparison to conventional pollination techniques.