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Ongoing project

New custard apple varieties and enhanced industry productivity (CU16002)

Key research provider: The Queensland Department of Agriculture and Fisheries

What’s it all about?

Beginning in 2018, this investment is responsible for:

  • The development and evaluation of new, high-yielding green and red skin custard apple varieties
  • Evaluating the performance of clonal and seedling rootstock selections
  • Delivering information and skills relating to crop management and production issues to Australia’s custard apple growers.

It has carried on the completed project Accelerating development of the Australian custard apple industry, new variety development and commercialisation phase 2 (CU13001).

The project team have continued work in the following areas:

  • Approximately 500 hybrid seedlings reached three years of age or greater in the 2019/20 season. These fruiting trees have been assessed for fruit set, vigour, yield and fruit quality.
  • Progeny that fruited in 2020 represented 27 different families, with seven new selections identified for propagation and further testing.
  • Data on vigour, yield and fruit quality from elite green and red skin selections was collected from regional small- and large-scale testing sites in Queensland and New South Wales.
  • The clonal propagation program in north Queensland has successfully developed rootstock that will be used in grower trials for industry evaluation.
  • Information and results continue to be extended to industry via newsletter articles and field days.

The project team continues to report good progress. Specific activities have included:

  • Approximately 1,000 hybrid seedlings from cross pollinations between elite red skin parents were germinated and potted, for planting in late spring.
  • All plants generated by project CU13001 over three years of age were assessed for leaf type, crop load and susceptibility to disease, with fruit from 16 individual progeny families assessed for fruit quality.
  • Elite red and green skin selections on small and large-scale grower testing have been assessed for vigor, yield and fruit quality.
  • A series of rootstock and variety trials were established in the previous phase of the project, with evaluation continuing for vigour, yield and fruit quality. Investigations include a long-term evaluation of root stock performance, an assessment of cuttings versus grafting, variety performance on clonal versus seedling rootstocks, and regional variety testing.
  • Progress continued with the clonal propagation program, with an increased number of motherstock to be made available to speed up multiplication.
  • New elite selections were grafted for on-farm testing, and will be distributed to grower sites for planting in spring.

The project team has shared progress with industry through several Custard Apple Australia events held in Alstonville, Bundaberg and the Glasshouse Maintains as part of the levy-funded project Custard apple communication and extension program (CU16001). Several articles were also published in the industry newsletter, The Custard Apple.

The research team have reported good progress on all four components of the project:

Regarding hybrid seedlings... 

Cross pollinations using elite parents from an earlier breeding program were carried out between December 2017 and March 2018, generating around 1,000 hybrid seedlings with elite red skin parents.

Hybrid seed was germinated on heat beds between March and July 2018. Trees that reached a suitable size and a good root system were field planted at high density in breeding blocks at Maroochy Research Facility. The rest will be planted out as they reach a suitable size.

Over 500 rootstock seedlings have been germinated and potted so new selections can be grafted for on-farm testing.

Regarding mature progeny evaluation...

Progeny populations generated in project CU13001, now three years of age, were evaluated for  leaf type and flower intensity. Fruit counts and quality evaluations will be carried out as fruit matures between December 2018 and May 2019. Progeny that has failed to fruit after four years will be culled from the project.

Regarding grower testing of elite selections...

Test sites for elite selections were visited for pruning and to collect data on early flowering and vigour ratings. All sites will be assessed for yield and fruit quality between February and May 2019.

Elite selections have performed well in most regions but at least another season of data will be needed before any recommendations for growers can be made.

Elite green and red skin selections were grafted in spring 2018 for distribution to growers in early 2019.

Regarding clonal propagation...

Clonal propagation of rootstocks and varieties for inclusion in field trials was carried out between September 2017 and May 2018. The collaborating nursery has reported successful clonal replication of most rootstocks, which will now be given time to mature

Still in its initial stages, this project is continuing to monitor and analyse the variety and rootstock trials planted during its predecessor, CU13001. It is also producing inter-variety crosses made from the best selection of red-skin atemoya types previously produced by the breeding program – with some 1000 seedlings expected to be produced during the 2017/18 and 2018/19 seasons, and field-planted for assessment at the project’s Maroochy Research Facility. Here there are currently around 1500 trees being held in breeding blocks, that are expected to fruit during the next two years.

From these variety trials, assessments will be based on production (natural early and late bearing cropping capacity) and precocity capacity (crop loading), fruit size, fruit symmetry, skin types, susceptibility to bruising, russetting, flavour, texture, seed number and seedlessness, fruit diseases shelf and storage life. There will be an emphasis on natural fruit production, flavour and external appearance.

There are two green-skin selections that progressed to large-scale on-farm testing during the previous project, which will reach maturity during the course of this project. Grower feedback will be incorporated with assessments for vigour, crop load, pest and disease susceptibility and suitability to different growing systems. This will provide the basis for a detailed report of potential new varieties and their suitability to different growing regions of Australia.

Other elite green-skin selections currently under small-scale testing across growing regions will also continue to be evaluated.

Related levy funds

This project is a strategic levy investment in the Hort Innovation Custard Apple Fund