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.

Developing new resistant varieties GCTCV119 mutagenesis

Latest update...

Unfortunately, in March 2018, tropical cyclone Marcus destroyed the GCTCV119 mutagenesis trial in the Northern Territory, with approximately 90% of the plant crop flattened. Work is currently underway in assessing the damage, with assessments likely to be delayed by 10 months.

Cyclone damage of GCTCV119 mutagenesis trial.

GCTCV119 overview

GCTCV119 is a Taiwanese Cavendish selection selected by the Taiwan Banana Research Institute (TBRI). It was developed using somaclonal selection from tissue cultured plants. Agronomic assessments at South Johnstone showed it didn’t perform as well as Williams Cavendish. It has a slower cycling time of approximately 15.1 months from plant to harvest, compared to Williams 10.6 months, and produces an average plant crop bunch weight of 20.4 kg, compared to Williams 29.1 kg. It is however known for its resistance to Panama disease tropical race 4 (TR4), and that is why it has been selected for mutagenesis. In the Philippines, better selections like GCTCV219 have been derived from GCTCV119. 

Trial progress

Mutagenesis, which is a breeding technique using gamma irradiation to increase  changes in tissue cultured plants, has been applied to cultivar GCTCV119. The aim is to improve the variety so that it retains tolerance to the disease and has improved agronomic 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 GCTCV119 was determined. 

GCTCV119 was irradiated and stabilised, and over a thousand plants were sent to the Northern Territory where they were held in the nursery prior to planting. Plants showing structural deficiencies were removed from the nursery and not included in the trial.

791 plants were planted into the field (inoculated with TR4) in June 2017. Williams Cavendish and GCTCV119 plants, which had not been irradiated, were also planted as control plants to compare against. 

Unfortunately, in March 2018, tropical cyclone Marcus destroyed the GCTCV119 mutagenesis trial in the Northern Territory, with approximately 90% of the plant crop flattened. Work is currently underway in assessing the damage, with assessments likely to be delayed by 10 months.

Example of tissue culture that undergoes gamma irradiation treatment.
Gammacell chamber used to apply gamma irradiation to banana tissue culture.

This trial is part of the Fusarium Wilt Tropical Race 4 Research Program (BA14014). 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.

Panama TR4 variety screening trial

TR4 variety screening trial

Panama disease tropical race 4 (TR4) is a major threat to the Australian banana industry. The availability of different varieties that are resistant to this soil borne disease is key to continuing to produce bananas in the presence of the disease. 

Variety screening trials have been established to assess the resistance of different banana varieties to Panama TR4. These trials are an important first step in finding a commercially acceptable alternative to the industry’s main variety ‘Williams’ Cavendish, which is very susceptible to the disease. 

The most recent variety screening trial conducted at the Coastal Plains Research Farm in the Northern Territory wrapped up in April 2018. This work was part of the research project, Banana Protection Program (BA10020) and results based on plant crop data are now available. Refer to the trial results below.

The new Improved Plant Protection for the Banana Industry (BA16001) project will continue this work with new trials at the site commencing in December 2018.   

About the trial

Conducted at the Coastal Plains Research Farm the trial was established on a site infested with TR4. In summary, the trial included:

    ⦁  27 varieties, planted in June 2016

    ⦁  plants artificially inoculated with Panama TR4

    ⦁  fortnightly disease ratings recorded

    ⦁  key agronomic characteristics of plant and first ratoon measured (time to bunching, bunch weight).

Method of trial assessments

All plants were artificially inoculated with colonised millet at planting. Four varieties with known response to Panama TR4 were used as references in the trial. These included:

    ⦁  FHIA-25 (Highly resistant)

    ⦁  Goldfinger (Resistant)

    ⦁  Formosana (Intermediate)

    ⦁  Williams (Very susceptible)

Assessments for the appearance of internal and external symptoms of the disease were undertaken on a fortnightly basis as well as at plant death or harvest.   

These assessments were undertaken on the plant crop as well as most of first ratoon plants. Unfortunately, in January 2018 a storm heavily impacted the trial three months prior to its intended finish. This meant that not all first ratoon information was able to be collected for all of the varieties. 

Coastal Plains variety screening trial (August 2017)
Coastal Plains variety screening trial after storm damage (January 2018)

The following categories were used to rank how susceptible or resistant varieties were to Panama TR4 in the plant crop.

Resistant (R): No disease symptoms were observed.

Intermediate (I): Majority of plants harvested with minimal plants showing symptoms or minor symptoms noted. With the appropriate crop management or environment to lower the inoculum levels these should be commercially viable. 

Susceptible (S): Majority of plants harvested with most plants showing disease symptoms.

Very susceptible (VS): Plants showing severe symptoms and >50% killed due to TR4 infection. 

Trial results

The following results of the plant crop have been reported by the project team as published in Australian Bananas Issue 52

Disease resistance ranking of plant crop

R = Resistant, I = Intermediate, S = Susceptible, VS = Very susceptible
* No disease observed, no signs of bunch at 12 months. 

Summary of results for plant crop

Where to from here?

The trial has produced some promising results, with four Cavendish varieties; CJ19, GCTCV 215, GCTCV 217 and Dwarf Nathan showing good resistance to Panama TR4 in the plant crop cycle. These varieties have been flagged as good candidates for mutagenesis. Mutagenesis is a breeding technique that uses gamma irradiation to promote changes in tissue cultured plants. The aim is to develop an improved variety that has commercially acceptable agronomic qualities, while maintaining its good resistance to Panama TR4. 

This trial work has already begun with CJ19 and Dwarf Nathan already undergoing mutagenesis. 

Future screening trials of new varieties will continue, with a new trial at Coastal Plains Research Farm due to commence in December 2018.  This work will be delivered as part of The New Improved Plant Protection for the Banana Industry (BA16001) project. 

Did you know...

In September 2017, several Far North Queensland growers visited the Northern Territory and saw the trial first hand.
The video below gives an overview of their visit and some of the grower’s impressions of the trial work being undertaken. 

This trial was part of the Banana Plant Protection Program (BA10020). This project was funded by Hort Innovation, using the banana research and development levy, and contributions from the Australian Government, with in-kind contributions from the Queensland Department of Agriculture and Fisheries, the University of Queensland and the Northern Territory Department of Primary Industry and Resources. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. 

Host research using Panama disease race 1

Host research using Panama disease race 1

Understanding what species are capable of hosting the fungal organism that causes Panama disease will help inform how weeds and ground covers are managed in areas infested with the disease. 

Work in Far North Queensland has used Panama disease race 1 as a surrogate for tropical race 4. Field surveys conducted in the region have identified plant species common to banana plantations that may act as potential alternative hosts. In this context, a host is defined as a plant in which the fungus can survive, often without obvious disease symptoms apparent.

Weed and ground cover species were collected from farms in Far North Queensland with a history of race 1 infection. In total 115 samples from 20 different plant species were analysed for the presence of the fungal organism (Fusarium oxysporum f.sp cubense) that causes Panama disease race 1. 

Roots from each of the plant samples were washed to dislodge excess soil before being surface sterilised. Segments of roots were placed in Fusarium selective media, and incubated for 3-5 days to allow fungal growth. The recovered populations were sent to a specialist diagnostic lab in Brisbane for formal identification. 

Race 1 was found living within four different species commonly found co-habiting Far North Queensland banana farms. These species were, spiny spider flower (Cleome aculeata), Youngia japonica, crowsfoot grass (Eleusine indica) and summer grass (Digitaria ciliaris).

Spiny Spider
Spiny spider flower
Summer grass
Summer grass
Youngia japonica
Crowsfoot grass

Please note...

Panama disease race 1 (R1) was used as a surrogate for Panama disease tropical race 4 (TR4), as access to TR4 infested banana properties in Queensland is restricted.

This trial was funded as part the Fusarium Wilt Tropical Race 4 – Biosecurity and Sustainable Practices project (BA14013). This project was funded by Hort Innovation, using the banana research and development levy, 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.

Host research using Panama disease subtropical race 4

Host research using Panama disease subtropical race 4

Understanding what species are capable of hosting the fungal organism that causes Panama disease, will help inform how weeds and ground covers are managed in areas infested with the disease. Using Panama disease subtropical race 4 (SR4) as a surrogate for Panama disease tropical race 4 (TR4), a glasshouse experiment was conducted in Brisbane to investigate potential alternative hosts of the fungus. In this context, a host is defined as a plant in which the fungus can survive, often without obvious disease symptoms apparent.

The glasshouse experiment included 18 species identified as being the most common species co-habiting Far North Queensland banana farms, or were regarded as high risk due to their presence on TR4 infested farms in the Northern Territory and Far North Queensland. The plants were inoculated with SR4, and their roots were analysed for the presence of the fungus after a period of 3 months. The roots from each of the plant samples were washed to dislodge excess soil before being surface sterilised. Segments of roots were placed in Fusarium selective media, and incubated for 3-5 days to allow fungal growth. The recovered populations were sent to a specialist diagnostic lab in Brisbane for formal identification.

Panama disease subtropical race 4 was recovered from all 18 species. The fungal organism that causes the disease was recovered from more of the sample plants of some species than others. Although the experiment showed that all species had the potential to host SR4, the differences in the frequency in which it was recovered suggests that some species more readily host the fungus than others do.  
Weeds included in glasshouse trials

Please note...

Panama disease subtropical race 4 (SR4) was used as a surrogate for tropical race 4 (TR4), as  SR4 is more closely related to TR4 than other races of the disease.

As seen in the figure above, Mullumbimby Couch had the highest disease recovery, with SR4 recovered from 80% of samples. Whereas Pinto Peanut had the lowest recovery, with approximately 16% of samples recovering SR4.
This trial is part of the Fusarium Wilt Tropical Race 4 – Biosecurity and Sustainable Practices project (BA14013). This project was funded by Hort Innovation, using the banana research and development levy, 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.

Alternative host research

Can weeds and ground covers host Panama disease?

The soil borne fungus Fusarium oxysporum f.sp. cubense (Foc) which causes Panama disease can survive and persist in the soil for years in the absence of banana plants. Weeds and ground covers that co-habit banana plantations can act as alternative ‘host’ plants. In this context, a host is defined as a plant in which the fungus can survive, often without obvious disease symptoms apparent.
 
By understanding what other species are capable of hosting Foc, it may change weed and ground cover management in areas infested with Panama disease. Keeping disease inoculum low is key to minimising spread to non-infected areas, and in the long term may play an important role in growing bananas in the presence of the disease.
 
So far, two complementary research efforts using Panama disease race 1 (R1) and subtropical race 4 (SR4) have begun to help our understanding of what weeds and ground cover species are capable of hosting Foc. This research has led to further trial work currently underway, including:
  • Understanding how Foc behaves within alternative hosts and whether it reproduces and has the ability to increase inoculum levels.
  • Publication of a guide that gives an overview of the plant species regularly observed in banana plantations and their ability to host Foc.
  • Investigation of weed and ground cover species in the Northern Territory using Panama disease tropical race 4 (TR4).

More information on trials...

This research was funded as part of the Fusarium Wilt Tropical Race 4 – Biosecurity and Sustainable Practices project (BA14013). This project was funded by Hort Innovation, using the banana research and development levy, 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.

Guide to crown end rot identification

Guide to crown end rot identification

Thielaviopsis musarum (commonly known as Chalara).
  • Rot extends beyond the crown and into the fruit (rapid development).
  • Usually limited to a few clusters.
  • Occurs randomly and mostly reported during winter and spring.
Thielaviopsis musarum
Fusarium equiseti-incarnatum species complex.
  • Gives a fuzzy/fluffy appearance on cut crown surface.
  • Usually causing cosmetic damage but incidence is often reported as high.
  • Reported to be worse during summer/spring. 
Fusarium equiseti-incarnatum species complex
Musicillium theobromae
  • Appearance not as fuzzy/fluffy as the above organism.
  • High incidence reported.
  • Reported to be worse during summer/spring.
Musicillium theobromae
Colletotrichum musae
  • Limited fungal growth apparent and sometimes orange spore masses are observed.
  • Rot can extend below the crown.
  • Low incidence reported.
Colletotrichum musae

Please note...

The above information is a guide only, as multiple organisms may be involved and simultaneously cause symptoms.  

If you notice any crown end rot symptoms or want further information, contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23. 

This work is funded as part of the Cause and management of crown rot of banana project (BA13011). This project is funded by Hort Innovation, using the banana research and development levy, 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.

Resistance to current post-harvest chemical trials

Resistance to current post-harvest chemical trials

Lab testing used to indicate whether a fungal organism has developed resistance to a particular post-harvest fungicide is commonly termed ‘sensitivity testing’. Sensitivity testing has been carried out on the two registered post-harvest products (prochloraz – Protak® and thiabendazole – Tecto®), against each of the four fungi known to be responsible for causing crown end rot (Fusarium spp., Colletotrichum musae, Musicillium theobromae and Thielaviopsis musarum, commonly known as Chalara). 
The fungal organisms listed above were collected from both Cavendish and Lady Finger fruit and from different growing regions including the coastal production area of Far North Queensland, the Atherton Tablelands and northern New South Wales.  Where possible the fungi were also sourced from fruit that had not been exposed to commercial management practices (backyard production) in order to provide a suitable comparison.

These results show that it may be necessary to change your post-harvest treatment products, depending on the organism/s you are having issues with and the location of your farm.

If you would like more information on this trial contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23.
This work is funded as part of the Cause and management of crown rot of banana project (BA13011). This project is funded by Hort Innovation, using the banana research and development levy, 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.

Time in supply chain studies

Time in supply chain studies

The length of time bananas spend in the supply chain can have a significant impact on the development of crown end rot (CER). 
Researchers conducted a simulation experiment, where Cavendish (Williams) and Lady Finger clusters were held 1, 2, 3 and 4 weeks prior to being ripened. The fruit for the experiments was sourced from a commercial property and all fruit was treated with a post-harvest chemical (prochloraz). To ensure a fair comparison, fruit from different positions in the bunch (top, middle and bottom hands) were assessed in case this was also a contributing factor. Once the fruit was ripened, the symptom development of CER was rated on a scale of 0-7 (7 being the most severe).

As seen in the graph below, the experiment with Cavendish fruit revealed fruit held longer within the supply chain resulted in relatively more severe symptoms of CER than fruit that would generally move through quicker. However, the overall symptom development was low as you can see in the graph below. 

Crown end rot ratings from the Cavendish time in supply chain simulation experiment (values with different letters are significantly different to each other)

As seen in the figure below, the simulation experiment using Lady Fingers showed similar results to Cavendish fruit in that fruit held for longer prior to ripening produced more severe symptoms of CER. However the overall symptom development was low as you can see in the graph below. 

Crown end rot ratings from Lady Finger time in supply chain simulation experiment (values with different letters are significantly different to each other)

If you would like more information on this trial contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23.

This work is funded as part of the Cause and management of crown rot of banana project (BA13011). This project is funded by Hort Innovation, using the banana research and development levy, 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.

Crown end rot

What is it?

Crown end rot (CER) of bananas is a serious cause of post-harvest quality loss for banana fruit. As the name suggests, the rot begins at the cut surface of the crown, and depending on the severity, can extend down the neck of the fruit and into the fingers. There are several fungi that can cause CER symptoms and the visual appearance of those symptoms may indicate what fungal organism is responsible. However, multiple fungi can simultaneously cause symptoms, so it can be difficult to distinguish the difference with the naked eye.

The following fungi can cause crown end rot in bananas:
  • Fusarium equiseti-incarnatum species complex
  • Musicillium theobromae
  • Colletotrichum musae
  • Thielaviopsis musarum (commonly known as Chalara). 
Crown end rot extending into banana fruit.

More info...

Click here for more information and photos of the symptoms typically associated with each fungal organisms.

How do you manage crown end rot?

Currently, the most effective management strategy for CER is the application of post-harvest fungicides. Products containing thiabendazole (e.g. Tecto®) and prochloraz (e.g. Protak®) are registered for post-harvest use in bananas.

Recent research has indicated that some of the organisms that cause CER are less sensitive to thiabendazole based products, particularly in the coastal regions of Far North Queensland. These organisms remain more sensitive to products containing prochloraz.  Simulation studies have also shown that the longer banana fruit is held in the supply chain before ripening, the greater the risk of developing more severe symptoms of CER. Research has also investigated alternative post-harvest products. 

See below for more information on this research.

More info...

This work is funded as part of the Cause and management of crown rot of banana project (BA13011). This project is funded by Hort Innovation, using the banana research and development levy, co-investment from the Department of Agriculture and Fisheries and contributions from the Australian Government. Hort Innovation is the grower-owned, non-for-profit research and development corporation for Australian horticulture.