What was it all about?

From 2016 until 2021, this investment supported a diverse and comprehensive breeding program to develop improved, quality varieties for the Australian citrus industry. A range of breeding technologies and germplasm work were employed within this integrated program.

The main highlight, as part of the Australian Citrus Breeding program, was the release and commercial adoption of two new mandarin varieties known as ‘Premier Murcott’ and ‘CB Murcott’. The development of these low-seeded varieties represents a concerted effort to combine attractive fruit appearance with good eating quality.

At project conclusion, more than 40,000 unique hybrids were growing in the field, representing genetic combinations aimed at the traits required for commercially successful new citrus varieties.

The project team worked across multiple requirements in support of the sector:

• Heavy focus was placed on achieving seedlessness, with multiple strategies tested. Work with a single gene for seedlessness demonstrated stability and effectiveness under Australian conditions and became the main breeding strategy, with most crosses in the final year of the project segregating for this gene. A new opportunity was discovered in one small family where approximately 50 per cent of progeny were seedless. This cross was repeated in higher numbers, along with other combinations using both parents, to better understand the mechanism involved.
• Orange breeding was an important component of breeding efforts, made possible by understanding the original sweet orange parents and availability of high quality pummelo to re-construct this citrus type. This work complemented the mandarin breeding activities with the opportunity to also recover citrus black spot resistance from this parent.
• Natural genetic disease resistance breeding work continued. All hybrids field-planted during the project were genetically resistant to Alternaria brown spot and citrus scab thanks to efficient screening techniques developed at Bundaberg. The program also successfully demonstrated natural resistance to citrus black spot in pummelo, and the ability to transfer this resistance to the program’s genetic pipeline via conventional hybridisation. Significant progress was made in capturing citrus tristeza virus resistance in scion breeding material and using molecular markers to incorporate additional disease resistance regions from Poncirus.

Australian citrus growers and industry are encouraged to contact the DAF Citrus breeding team or Hort Innovation if they would like more information.