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Ongoing project

National papaya breeding and evaluation program (PP18000)

Key research provider: Griffith University

What’s it all about?

New red and yellow papaya varieties are continuing to be bred and evaluated under this program, which follows on from the investment New genetic targets to improve quality in papaya (PP15000). The research team is focused on delivering new elite, genetically stable cultivars that meet the needs of growers and the preferences of consumers, and that are adapted to key growing areas in northern Queensland, including the Tableland and coastal regions. The ultimate goal is to expand the marketability and profitability of the Australian papaya industry.

Following the investment Technical review of the national papaya breeding and evaluation program (PP18002), new recommendations have been incorporated into PP18000. This has seen sensory work added as a new component, which involves using professional taste panels and flavour mapping in collaboration with the University of Queensland, to support the development of premium varieties and drive consumer acceptability and preference for Australian papaya.

There review also recommended work to access more international germplasms to broaden genetic diversity, especially in red-fleshed varieties.

Since the project team’s last update, work has progressed in the breeding, selection, and ongoing assessment of advanced red and yellow papaya lines and F1 hybrids.

A total of 240 seedling of F6 red generations were field planted on two trial sites in Innisfail (Zappala Farm and RMC Farming). Evaluations were completed for both sites in October 2021 and February 2022. Outcomes demonstrated that:

  • The advanced breeding lines grew fruit significantly closer to the ground than RB1.
  • The trunk circumference (cm) of the advanced breeding lines (F6 generation) was not significantly different to RB1.
  • The Zappala site produced lower numbers and smaller sizes of side shoots than RB1, however the same was not observed for the RMC site.

The F5 advanced breeding lines of yellow papaya were field planted at two trial sites in the Tableland (Lecker Farming and Rocky Top Farm). The first evaluation was completed at both trial sites showing the Lecker Farming site set fruit significantly lower than the commercial cultivar 1B, and the Rocky Top site set fruit significantly lower to the ground than all of the breeding lines (except Lecker Farms). Another 120 are to be planted at Lecker Farms in March-April 2022.

Progress has also been made towards the award of Plant Breeder Rights (PBR) protection of the advanced breeding lines and new hybrids.

Progress continues on the international germplasm collection, and activities relating to potential trait introgression.

Since the project team’s last update, work has progressed towards providing genetically stable and superior varieties (F7 and F1 hybrids) to the industry.

  • Evaluation of fruit quality and tree productivity on F5 red papaya was completed at the two Innisfail trial sites. Overall, the advanced red breeding lines performed better than the standard red variety (RB1) with fruit set lower to the ground, higher ºBrix, higher yield, more cylindrical shape, and fruit size of 800-1100g.
  • The production of F6 generation advanced breeding lines of red papaya was achieved. These will be field planted at Innisfail in April-May 2021 and at Tablelands in August 2021.
  • Yellow papaya F5 seedlings were sex determined and will be field planted in March 2021. Planting was delayed due to poor weather conditions.
  • The team plan to assess pre- and post-harvest disease reactions of the advanced breeding lines for black spot (Asperisporium caricae), brown spot (Corynespora cassiicola), Phytophthora fruit and root rot (Phytophthora palmivora), Phytoplasma disease (Candidatus Phytoplasma), anthracnose (Colletotrichum gloeosporioides), stem end rot (Lasiodiplodia theobromae), Phomopsis caricae-papayae, Mycosphaerella spp. and Phytophthora palmivora), and papaya sticky disease (Umbraviruses, papaya meleira virus 2).
  • To broaden the genetic base of Australian papaya, seed from diverse sources was obtained under material transfer agreements and biosecurity protocols from Malaysia, Taiwan and Thailand. Eleven varieties were field planted during 2020 at a Tablelands trial site for evaluation. Further germplasm from Philippines and varieties from Thailand have been identified and import procedures commenced.
  • The team provided regular reports on research progress to industry through bulletined updates and industry meetings.

The project team are progressing their efforts in key areas of this long-term investment.

Advanced breeding of red and yellow papayas

A questionnaire was delivered to industry to gain a better understanding of production costs, from field preparation to transport to wholesale. Interviews with fruit agents were conducted at Brisbane market to also understand marketers’ perspectives on the preferred characteristics to increase fruit sale. This information was then consolidated to formulate a weighted selection index for papaya breeding targeting fruit quality.

Breeding lines were selected from trees at two trial sites where the trees exhibited fruit set lower to the ground, a trait required for ease of harvest and higher yield.

The selected trees were subsequently self-pollinated to produce F5 generations. These will be evaluated, selected, and self-pollinated to produce F6 generations by the end of 2020, towards F7 seed being produced by 2021.

The project team is collaborating with the Queensland Department of Agriculture and Fisheries (QDAFF) to evaluate common major papaya field diseases for the new advanced breeding lines.

Flavour and sensory analysis by trained panel

The project team has partnered with the Centre for Nutrition and Food Science within Queensland Alliance for Agriculture and Food Innovation (QAAFI) at the University of Queensland to identify flavour profiles of the main commercial varieties and the new breeding lines.

Two sensory studies were successfully carried out over two harvest periods in September 2019 (winter/spring fruit) and January 2020 (summer fruit) with the key findings to inform the breeding program.

To protect the newly developed genetically stable varieties, Plant Breeders’ Rights (PBR) will be applied for selected F7 lines.


Read more about this program in the project updates published in the Papaya Press magazine: