Leucaena (Leucaena leucocephalassp. glabrata) is one of the most widely sown pasture legumes in the tropical and sub-tropical areas of Queensland. Estimates of the total area established exceed well over 220,000 ha. Where suited, this leguminous tree is the basis of a highly productive and persistent pasture. Technologies have been developed to address issues with establishment, grazing management and the risk of toxicity. As with most successful, introduced pasture plants, there are concerns about the weed risk associated with seed spread from stands of forage leucaena into non-grazed areas, especially areas of environmental significance such as waterways. Prior to its widespread use as a pasture plant, leucaena plants (most likely the so-called common species of leucaena, L leucocephalassp. Leucocephala) had already colonised pockets of ungrazed, non-agricultural land along urban and coastal locations of Queensland and some other areas of northern Australia.
This has served to raise concerns about the potential for pasture plantings to exacerbate this problem. Critical to the ongoing success of this species is the need to ensure that new initiatives such as the development of a sterile variety of leucaena are both technically feasible and likely to be accepted as addressing concerns regarding the weediness of this species such that they may be broadly adopted by producers. Concerns regarding the weediness or perceived weediness of leucaena have led to this aspect having prominence in the code of practice for leucaena growers promoted by the Leucaena Network . This report evaluated the technical feasibility of developing sterile leucaena using two contrasting methodologies: genetic modification and hybrid breeding systems and the likelihood that these methodologies could develop cultivars that address the concerns regarding invasiveness in leucaena.