Developing new resistant varieties
Goldfinger mutagenesis trial

Latest update...

The evaluation of the Goldfinger variants with improved tasting characteristics from the mutagenesis program is continuing at South Johnstone. 

Our variety researchers will soon shortlist to just 4 or 5 of the best performers from the plant crop for more detailed post-harvest assessments in the ratoons. Three of the better performers so far are pictured below. 

The 20 variants have all been established back into tissue culture at DAF’s Maroochy laboratory so that they can be sent to the NT to validate that they have retained TR4 resistance.

Three of the better performers from the 20 Goldfinger selections

Goldfinger overview

Goldfinger (FHIA-01) which was bred by the Honduran Foundation for Agricultural Research (FHIA) is a non-Cavendish dessert banana variety that is highly resistant to Panama disease tropical race 4. 

Variety evaluation work previously conducted at South Johnstone has shown the agronomic performance of Goldfinger rates relatively well when compared to Williams. Average bunch weight of plant crop was heavier for Goldfinger at 34.3 kg compared to Williams 30.5 kg. However, the variety had a longer cycling time at 14.4 months from planting to harvest, compared to 12.4 months for Williams. Although it is a reasonably productive variety, improvements are sought in fruit quality characteristics. 

Goldfinger trial block at the South Johnston Research Station (January 2018)
20 Goldfinger selections included in second stage trial block (July 2020)

Trial progress

Mutagenesis, which is a breeding technique using gamma irradiation to promote changes in tissue cultured plants, has been applied to the cultivar Goldfinger. The aim is to develop an improved variety which retains its tolerance to the disease and has improved fruit quality characteristics. 

The first step in this process was to determine how much gamma irradiation to use on this variety. Too much irradiation can severely damage or kill the plant, and too little may not induce sufficient changes to the plants.

Experiments, known as dose response trials, have been conducted at the Maroochy Research Station and the sufficient dosage for Goldfinger was determined.

630 irradiated Goldfinger plants were sent to South Johnstone Research Station, in two batches during June and August 2017 where they were held in the glasshouse prior to planting.

They were planted in the field in September and November 2017 respectively. Goldfinger plants which hadn’t been irradiated were also planted as control plants to compare against.

Irradiated plants in the field showed considerable variation in vegetative characteristics. This variation is mostly related to degree of dwarfness/plant height, pigmentation of pseudostem/leaf stalk and midribs, leaf uprightness/droopiness and minor leaf deformities. Also some of the irradiated plants have gross plant/leaf deformities and extremely slow growth. About 13% of the irradiated plants are currently in this reject category. 

Harvest of both the September and November 2017 plantings were completed by the end of 2018. The photos above show the very large range in bunch and fruit characteristics which have been obtained by irradiation. Yes they have all come out of Goldfinger!

Postharvest assessments also revealed diversity in the eating quality of the  Goldfinger variants. Several had qualities considered to be ‘improved’ and ‘better’ than the standard Goldfinger, including increased sweetness and firmness. Taste-testing sessions held amongst the staff at the research station were used to gauge consumer acceptance of these variants.  

Agronomic and post-harvest assessments are now complete, with 20 better tasting Goldfinger variants selected for a second stage of testing. Sucker and bit material from selected variants was prepared and 10 plants per selection were established. Planting of this second trial stage occurred in September 2019.

Bunch emergence in the stage two trial block began in March 2020 and is continuing. Harvest will be completed in December 2020. Researchers will soon shortlist to just 4 or 5 of the best performers from the plant crop for more detailed post-harvest assessments in the ratoons 

The 20 variants have all been established back into tissue culture at DAF’s Maroochy laboratory so that they can be sent to the NT to validate that they have retained TR4 resistance.

Material will also be sent to Sharon Hamill and her team at Maroochy Research Facility to go back into tissue culture. Plantlets will then be sent to the Northern Territory to be screened against Panama disease tropical race 4 to ensure the original resistance of Goldfinger has been retained. 

Example of tissue culture that undergoes gamma irradiation treatment.
Gammacell chamber used to apply gamma irradiation to banana tissue culture.
Taste test survey
Postharvest quality assessments use the Brix scale to measure the sugar content of fruit.

Goldfinger variety research features on ABC's Catalyst program

Check out ABC’s Catalyst story on banana production and the work that’s underway to find a new variety; a variety that can match our love for Cavendish while also having good pest and disease resistance. Paul West speaks with Cameron Mackay and banana researchers Jeff Daniells and Stewart Lindsay to find out more. 

Examples of variation

Normal Goldfinger bunch (unirradiated).

Goldfinger bunches (irradiated) – Variations as a result of mutagensis.

Left is control that didn't undergo mutagenesis. Variant on the right has undergone mutagenesis and shows dwarfism and more upright leaves.
Left is control that didn't undergo mutagenesis. Variant on right shows changes to plant pigmentation as a result of mutegenesis.

More information...

This Goldfinger work was initiated as part of the Fusarium Wilt Tropical Race 4 Research Program (BA14014). At the close of BA14014 funding has been provided through the Improved Plant Protection for the Banana Industry Program (BA16001) for continuation of the evaluations.   This project has been funded by Hort Innovation, co-investment from the Queensland Department of Agriculture and Fisheries, and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.