Breeding new rootstocks for the Australian citrus industry (CT18004)

What was it all about?

From 2018 to 2024, this investment developed new rootstocks for the Australian citrus industry that are truly innovative, unique and outperform existing material. 

New germplasm was created, heavily screened for disease resistance and local adaptation, and then tested under commercial conditions.  By properly addressing long standing Australian production issues such as citrus tristeza virus (CTV), phytophthora and salinity, it was then possible to consider the far more challenging issues of huanglongbing (HLB) disease and vigour control.  This was made possible via a two-pronged breeding strategy of purposeful parent selection and large-scale hybrid generation and screening.

Once breeding and screening work was completed, the successful hybrids were then included in large field trials located on commercial properties, in order to determine field adaptability.  Tree health, vigour, and fruit quality were assessed every season at these extensive on-farm trial sites.  This information was used to guide future parent selection so that there could be constant improvement in the choice of parents within the breeding program.  This strategy of regularly planting large field trials has provided the breeding team with a constant flow of new information that can be immediately captured in the hybridising program.

The project is the first in the world to demonstrate that Australian wild citrus species can be used as parents to produce new rootstock hybrids whose performance is comparable to current conventional options. This has attracted international attention as a possible strategy in the fight against HLB disease.  It provides industry with greatly expanded options in terms of genetically diverse rootstocks that could be deployed if they show future disease tolerance.  Many of the problems currently facing world citrus production are a consequence of genetic monocultures, and this project has demonstrated how this issue can be addressed efficiently and with rapid industry applicability.

New information on disease resistance and segregation has been developed, and rapid molecular screening techniques have been validated on Australian rootstock breeding populations. Conversely, the project has also shown that there is no substitute for long-term field trials prior to commercial release.  These extensive field trials have identified a subset of unique hybrids with robust performance warranting wider commercial evaluation.  New and unique germplasm has been created, providing long-term opportunities for the Australian industry to increase genetic diversity using high-performing rootstock options.