Evaluation of new rootstocks for the Australian citrus industry 2017-2022 (CT17002)
What’s it all about?
This investment is evaluating the performance of new rootstocks for the Australian citrus industry, with a focus on improving the yield and quality of both fresh and processing fruit, boosting tree health by improving tolerance to stresses, and looking at the modification of tree architecture.
The goal is to deliver superior and locally-adapted rootstocks to Australian growers, suited to both mainstay and new citrus varieties. The work will ultimately allow growers to intensify plantings, modernise orchards and obtain higher yields with minimal extra inputs, while meeting requirements for existing and emerging markets.
This iteration of rootstock continues work from the concluded Evaluation and commercialisation of new citrus rootstocks (CT13042). This means it is…
- Continuing the evaluation of the industry’s new, high-performance Chinese rootstocks. As a result of earlier evaluation work, six new rootstocks were released to industry in 2017 (Zao Yang, Tanghe, Ghana, Donghai, Anjiang hongju and Caoshi xiangju), and their evaluation will be ongoing through this project. They are currently planted in grower trials across 12 orchards in New South Wales, Victoria, South Australia, Queensland and Western Australia. (A reminder that information on these rootstocks remains available on the NSW DPI website here.)
- Continuing dwarfing citrus rootstock trials, established at the evaluation program’s Dareton field site in New South Wales during September 2017. These involve semi-dwarfing Chinese rootstocks as well as dwarfing rootstocks imported from the United States, on which M7 navel, Atwood navel and Tang Gold mandarin are being grown.
- Continuing evaluating rootstocks for salt tolerance, through a trial taking place in Western Australia. Established in 2013, the research team report that the trees are now productive and data on yield, fruit quality and tree health will now be collected over the project’s years.
- Continuing trials involving processing oranges in the Riverina region of New South Wales.
New work in the project includes…
- Establishing a field trial at the project’s Dareton site to evaluate the performance of rootstocks imported from Italy.
- Identification of Huanglongbing-tolerant rootstocks for importation and subsequent field trials to assess their performance in key growing regions. This particular work will involve collaboration with Auscitrus and state departments.
Since November 2019, the project team have progressed with the following activities:
- Trees for the Italian rootstocks are now planted. A new trial has been established at New South Wales Department of Primary Industry Dareton to evaluate the effect of the Italian rootstocks on fruit yield, fruit number, fruit size distribution, fruit weight, fruit quality, acidity and juice content. Tree health will also be assessed by recording graft union compatibility with Imperial, Nectar and Tang Gold mandarin scions.
- Data for the salt tolerant rootstock planted at Bindoon in Western Australia was collected and reported. This trial was established in October 2013 and the trees are now productive. Data for tree growth, fruit quality, acidity, juice content and fruit yield will be collected for a further four years, prior to making industry recommendations and releasing the most promising rootstock(s).
- The Huanglongbing-tolerant (HLB) rootstock trials have been delayed due to Covid-19 restrictions.
The project team continues to share findings with industry as they become available, with it anticipated that project results will be presented at the Citrus Australia Technical Forum in 2021.
This long-term investment continues across multiple trial programs to evaluate the performance of several new rootstocks for the Australian citrus industry.
Since May 2019, the project team have:
- Assessed tree health on all trial and grower sites, with no diseases found. Tree health and bud unions continue to be monitored.
- Completed fruit harvesting at the Riverina trial of new high-performance Chinese rootstocks, with data recorded for tree growth, crop yield and quality. The season’s results indicated that trees on Zao Yang rootstock had slightly larger tree heights, larger tree circumference, higher yields, and fruit weight compared to other rootstocks. As an ongoing trial, findings are not conclusive at this stage.
- Maintained the young trees in the dwarfing citrus rootstock trials at Dareton field site in New South Wales. Established in October 2017, tree growth is progressing well and fruit at harvest time was removed to establish the tree canopy. Preliminary observations regarding tree growth and diameter have been made but no conclusions can be drawn at this early stage of the trial.
- Established grower trials for Navel, Valencia, Mandarin and Eureka lemons at properties across five Australian States. A range of rootstock have been selected, based on potential compatibility to different scions and soil type suitability.
The project team continues to share findings with industry as they become available, with ongoing engagement across the sector.
Work is progressing including…
Trees propagated for Italian rootstock trial
Rootstock seedlings of Italian hybrid varieties F5P12, F6P12 and F6P13 have been introduced by ANFIC Nurseries. These rootstock hybrids have performed well under Italian growing conditions, producing high yields of good quality fruit. The new rootstocks will now be tested under Australian conditions and planning for a trial at NSW DPI Dareton has begun. Tree health will also be assessed by recording graft union compatibility with Imperial, Nectar and Tang Gold mandarin scions.
Rootstock seedlings were raised last year, and the Italian rootstocks are now budded to three scion varieties: Imperial, Nectar and Tang Gold mandarin. The trees will be ready to be planted in Oct/Nov 2019 and the trial design has been decided.
Salt tolerance trial
A salt tolerance trial established in October 2013 now has trees in productive stage, and initial measurements have been taken. The trees are 17 different rootstocks including four Chinese rootstocks (Zao Yang, Anjiang hongju, Caoshi xiangju, Zhoupi jiangjin), five Scarlet mandarin x Poncirus trifoliata hybrids from the NSW DPI Gosford breeding program, and three Sunki mandarin x P. trifoliata hybrids and one Rangpur Lime x P. trifoliata hybrid from the USDA breeding program. Rangpur Lime, Sunki mandarin, Swingle citrumelo and Troyer citrange serve as comparison (control) rootstocks. Trees are managed according to local district best practice.
The data for tree growth, fruit quality, acidity, juice content and fruit yield will be collected for a further four years before making industry recommendations and releasing the most promising rootstocks to industry.
The project leader reports that the rootstock evaluations are on track with progress on….
- Experimental trials planted in October 2017 in five states, which are going well with tree height and diameter measures due in 2019.
- Two dwarfing rootstock trials, established at Dareton in the same month, with a total of nine different rootstocks in each trial with M7 navel and Tang Gold mandarins. The trees are also doing well.
- Riverina Valencia trials continuing, with data on tree growth, yield and quality now collected for 2017 growing season. Zao Yang rootstock has shown superior yields so far (30.8 kg/tree compared with 25.4 kg/tree for standard Tri22), but data from future seasons is needed to confirm this over time.
- Communication efforts have seen the research featured quite heavily in the media including ABC radio and TV, and in rural papers, as well as at field days in NSW and Victoria, as well as at a conference in Portugal among others.
This project is a strategic levy investment in the Hort Innovation Citrus Fund