National citrus scion breeding program (CT00012)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

The National Citrus Scion Breeding program was a long-term program that had been supported by the Australian Citrus Industry since 1991 through a series of discreet one-to-four year projects funded by Hort Innovation (which was then Horticulture Australia Limited) and the research providers CSIRO Plant Industry and DPI&F Queensland. Since 1996 the program had been funded as a fully coordinated project with research focused in four main areas of activity, namely conventional diploid hybridisation (CSIRO Plant Industry, Merbein), the production of triploids for seedlessness (DPI&F Queensland, Bundaberg), mutation breeding (Merbein and Bundaberg) and gene technology (CSIRO Plant Industry, Adelaide).

The development of new scion varieties through breeding, selection and introduction was a high priority for the Australian Citrus Industry. The National Citrus Scion Breeding Program was focused to address industry priorities for new fresh fruit varieties. Major characteristics targeted were seedlessness, easy peel, flavour and size, internal and external quality, and agronomic characteristics such as ease-of-harvest, amongst others. The breeding program aimed to produce new varieties adapted to Australia's varied regional conditions and the research had been designed to provide marketing, processing and production advantages to the Australian Citrus Industry.

Key outcomes of the program were the adoption of innovative new varieties that addressed the needs of key industry identified market windows of opportunity resulting in increased profitability for Australian citrus growers. Key windows of opportunity identified during project CT00012 were for early and late maturing, seedless, sweet, easy-to-peel varieties primarily for export.

General conclusions from the project were that the program was producing results that would have application to industry in the form of new varieties, as well as results that were having immediate application to the breeding program itself. In terms of results for industry, data from second stage evaluation trials being conducted on grower-based regional test-plots were indicating that a nomination for release of two new seedless easy-peel varieties would most likely occur in late 2005. Results impacting on the program itself included data on the inheritance of key traits and improved breeding and screening methods. Increased numbers of triploid hybrids produced during CT00012 was an important project output that impacted on future directions taken at Bundaberg.

With regard to future R&D, evaluation of new variants and selections in replicated plantings were key components of the project. In addition, as selections showed promise in regional test-plots, it was important to progress the most promising to larger scale evaluation blocks of 0.5-1.0 ha so that sizable volumes of fruit would be available for test marketing. Market-testing was important for when new varieties were released. These larger trials were initiated prior to commercial release so that fruit was available to test markets while commercial plantings were established and before large quantities of commercially-grown products were available. Other areas for future R&D were to resurrect the biotechnology component of the project, which was suspended during the course of CT00012. This may have been achieved through exploring and developing mutually beneficial overseas collaborations. With the success shown in irradiating parthenocarpic Kara mandarin to give two seedless lines, further consideration needed to be given to entering high quality parthenocarpic hybrids that were capable of setting seedless fruits in the absence of pollination into a mutation program as well. Such hybrids, due to self-compatibility, were normally seedy in an open-pollination situation. Irradiation could result in eliminating seeds in these hybrids giving them potential for progression to regional evaluation and ultimately variety release. Industry was involved with the project by evaluating selections from the program under testing agreement so that regional adaptability could be assessed. Practical application of the research to industry occurred when new varieties were released from the program.