Building a genetic foundation for Australia’s citrus future through targeted breeding (CT15017)
What’s it all about?
Beginning in late 2016, this project supports a diverse and comprehensive breeding program to develop improved, quality varieties for the Australian citrus industry. A range of breeding technologies and germplasm work are employed in this integrated program.
The project team reports that all aspects of the breeding project are progressing well. Recent efforts have focused on assessing trees that fruited during 2018, to pinpoint the best families, incorporate better parents into the pollination plan, and to cull a substantial number of poor-performing families.
Key outcomes of the project since last update have included:
- The new hybrid selections were propagated on healthy rootstocks in August 2018, and the most vigorous of these nursery trees were field planted in early December 2018. Slow growing propagations have been retained in the nursery and will be planted in late summer.
- Seedlessness is one of the traits that is sought, and the team has found a potential new source. They are aiming to breed seedless trees that also have other desirable characteristics to produce superior varieties.
- All commercial testing blocks have been established, locations and layouts clearly documented and secured, and field plans updated as tree losses are replanted with new trees.
- New rootstock seed has been sown, new selections budded and a high standard of nursery management applied to material at all stages within the breeding program. The mixture of rootstocks now being employed to support this scion breeding program has been influenced by outcomes from the breeding teams associated rootstock development efforts (such as the Queensland citrus improvement scheme: finding better rootstocks for Australia (CT13004) project).
- Because citrus is attacked by more diseases and pests than any other tree crop, genetic resistance to pests and diseases is another aim of the breeding program, with varieties tested for resistance to alternaria, black spot and citrus scab, among others. The team’s success in breeding for alternaria and citrus scab resistance is already recognised internationally, and they hope to publish similar success with black spot resistance in the coming months.
Below is an update recently provided to Hort Innovation by the breeding project team…
The project is on track to deliver varieties that are excellent in both appearance and taste, with large-scale commercial test sites now well established and beginning to fruit. These sites are starting to provide the necessary information to allow full commercial availability of these selections. Improved selections of this material may also become available once fruit are assessed, with assessments due to take place in July 2018.
The challenge of producing seedless varieties is a key focus of the project’s pollination program [during the flowering season, the pollination program focuses on parent combinations now known to produce hybrids with the best fruit quality, or on combinations with parents containing traits new to the program]. Climatic conditions were more favourable during the 2018 flowering season, and most of the desired crosses were made. Subsequent fruit set has also been promising and the first of the hybrid seed is now being sown.
The program’s long-standing commitment to disease resistance breeding is delivering multiple benefits including the establishment of large progeny blocks of genetically resistant hybrids from which future new varieties can be selected. Requirements for chemical sprays have been greatly reduced, despite climatic conditions highly conducive to disease development.
A broad-based pollination plan was developed and executed, capturing all of the stated objectives of the breeding program. Disease-screened hybrids have been field planted, and disease levels remain low in all progeny blocks.
This project is a strategic levy investment in the Hort Innovation Citrus Fund