Gene identified for full virulence of the Fusarium wilt towards Cavendish banana

In an article in the PLOS One journal researchers identified a gene and protein that is required for full virulence of the fungus that causes Furasium wilt in Cavendish banana. A mutant of the Fusarium oxysporum f.sp. cubense (Focub) SIX1a gene was tested in the banana plant. This mutant was found to be severely compromised in its virulence. When the gene was reintroduced virulence was restored to wild type levels.

More about the research in the PLOS One article ‘A SIX1 homolog in Fusarium oxysporum f.sp. cubense tropical race 4 contributes to virulence towards Cavendish banana.’

 

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New publication on improving banana cultivation

Recent research on improving banana cultivation is bundled in the new publication ‘Achieving sustainable cultivation of bananas Volume 1’. Both the banana research community as well as banana producers will find information from all over the world about the current challenges in banana production, improving cultivation practice across the value chain, from propagation to harvesting, packaging and ripening, and ways of measuring and improving the environmental impact of banana cultivation.

Throughout the book attention is paid to pests and diseases affecting bananas, including Fusarium wilt. Highlights of the book include: the latest research on banana domestication and genetic diversity; new research on the limitations of current good agricultural practices and how areas such as soil health can be improved; and summaries of best practice in neglected but critical areas such as harvesting and ripening operations.

More information and the opportunity to order the book at the publishers website.

https://shop.bdspublishing.com/checkout/Store/bds/Detail/WorkGroup/3-190-55859

 

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How can we protect bananas?

The Biomedical Science Journal for Teens has put research into banana Black Sigatoka disease in the spotlight. The disease is threatening commercial Cavendish banana crops worldwide, as the fungus that causes it has developed resistance to the chemicals that are supposed to control them. Researchers also detected a specific protein in the fungus, that triggers the resistance mechanism of the plant. These yet unknown disease resistance genes could be used to save the banana industry.

In order to further support the sustainable production of bananas researchers wanted to find out more about the genetic basis of disease resistance to Pseudocercospora fijiensis strains, which cause the Black Sigatoka or “black leaf streak disease” (BLSD). Researchers isolated the DNA of the fungus, sequenced its whole genome and built a genetic map to complete the genome picture to better understand the relationship between the banana and its pathogen.

Also, they found a gene that is coding a protein, a so-called effector protein, which triggers a resistance mechanism in wild bananas. Upon recognition, the plant kills the infected cells and surrounding cells, thereby stopping the spread of the infection. Bananas recognizing this protein most likely possess a resistance gene. This could greatly help banana breeding and production.

Less bananas due to reduced photosynthesis

When bananas are affected by BLSD, the fungus destroys the leaf tissue which reduces photosynthesis and thus, crop yields. Farmers can control BLSD only through fungicides, and this greatly increases the economic and environmental costs to produce bananas. Moreover, the frequent use of fungicides leads to strains that are increasingly resistant to these chemicals.

Further reading

Read the whole article in Science Journal for Kids

http://www.sciencejournalforkids.org/uploads/5/4/2/8/54289603/fungus_genome_article.pdf

The article is based on the PLOS genetics article: ‘Combating a Global Threat to a Clonal Crop: Banana Black Sigatoka Pathogen Pseudocercospora fijiensis (Synonym Mycosphaerella fijiensis) Genomes Reveal Clues for Disease Control’ http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005876

 

 

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Secret sex life of fungus extends value of resistant wheat for food production


Kema and co-workers recently published an article in the prestigious Nature Genetics journal on the sex life of Zymoseptoria tritici, the causal agent of septoria tritici blotch in wheat, the most important wheat disease in Europe and North Africa (Nature Genetics 50, 375–380, doi:10.1038/s41588-018-0052-9). They showed that avirulent isolates of the fungus do not disappear from the natural populations, but actively engage in sexual reproduction, thereby retaining their genes in the population. This results in a slow decline of resistance in wheat crops and also explains why resistance to strobilurin fungicides boomed in natural populations. The fungus is a close relative of Pseudocercospora fijiensis, the causal agent of black Sigatoka in banana. Both belong to the Dothideomycetes and therefore, the newly discovered aspects on the reproductive biology of this fungus may well apply to many more fungi, including P. fijiensis.  This is important in any future breeding strategy for bananas.

Full publication (Subscription or payment may be required): Stress and sexual reproduction affect the dynamics of the wheat pathogen effector AvrStb6 and strobilurin resistance

 

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World-first Panama disease-resistant Cavendish bananas

Researchers from Queensland University of Technology in Brisbane, Australia, have designed genetically modified Cavendish bananas with resistance to the devastating soil-borne Panama disease. This disease is caused by the fungus Fusarium oxysporum f.sp. cubense Tropical race 4 (TR4) and also known as Fusarium wilt of banana. Scientists from Wageningen University & Research in the Netherlands validated the field data.

In the world’s first field trial with genetically modified banana plants conducted in heavily TR4-infested soil, one Cavendish line transformed with a gene taken from a wild banana remained completely TR4 free, while three other lines showed robust resistance. The results have just been published in Nature Communications.

The team cloned the so-called RGA2 gene from the wild progenitor of edible bananas, Musaacuminata ssp. Malaccensis, which has a remarkable resistance to TR4. One modified Cavendish line (RGA2-3) remained TR4-free for the three years of the trial. Three other lines modified with RGA2 showed strong resistance, with 20% or fewer plants exhibiting disease symptoms over a period of three years. In contrast, 67% to 100% of the control bananas were either dead or heavily TR4-infected after three years, including the Giant Cavendish somaclonal variant 218, currently heralded as being resistant to TR.4.

Running from 2012 to 2015, the field trial was led by Distinguished Professor James Dale from Queensland University of Technology. It was conducted on a commercial banana plantation outside Humpty Doo in the Northern Territory in Australia previously affected by TR4. The soil was also heavily reinfested with disease for the trial.

“Absolute breakthrough”

The research team of Gert Kema, professor in tropical phytopathology at Wageningen University & Research, partnered in the project. “The GM banana lines show that the activity of the RGA2 gene is strongly correlated with the level of resistance to TR4,” comments Kema. “This is an absolute breakthrough as it concerns the first identified resistance gene to Fusarium wilt. However, this is only the start – some light at the end of the tunnel. The next step is to deploy the immense diversity in wild bananas to diversify the fruit and establish a resilient and sustainable banana production for all. In 2012, we determined that this banana species has valuable resistance to TR4 and Professor Dale’s group has now confirmed this by cloning the underlying gene. Our role was to validate the fungal infections using the molecular techniques that we developed to detect and quantify TR4.”

While Cavendish bananas have been found to also have this RGA2 gene naturally, it is not very active in susceptible plants. New research is looking at how to ‘switch on’ the gene in Cavendish bananas to make them TR4 resistant.

The researchers have begun an expanded field trial on the same plantation, growing the four resistant RGA2 lines and newly developed lines of modified Grand Nain and Williams Cavendish varieties. They have the capacity to screen up to 9,000 plants for resistance and to determine yields and other important traits over the coming five years.

The article, Transgenic Cavendish bananas with resistance to Fusarium wilt tropical race 4, can be accessed here.

 

For further information, please contact prof. Dr. Ir. Gert Kema tel 00 31 317 480632 or by e-mail: gert.kema@wur.nl

 Co-authors with Professor Dale are Professor Gert Kema, Fernando Garcia-Bastidas (Wageningen University & Research, the Netherlands), Dr Anthony James (QUT), Dr Jean-Yves Paul (QUT), Dr Harjeet Khanna (Sugar Research Australia, formerly QUT), Mark Smith (Darwin Banana Farming Company), Dr Santy Peraza-Echeverria (CICY, Mexico, formerly QUT), Professor Peter Waterhouse (QUT), Distinguished Professor Kerrie Mengersen (QUT) and Professor Robert Harding (QUT).

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Article on The conversation covered by CNN

Ioannis Stergiopoulos, Assistant Professor of Plant Pathology, University of California, Davis; André Drenth, Professor of Agriculture and Food Sciences, The University of Queensland and Gert Kema, Special Professor of Phytopathology, Wageningen University wrote an article for ‘The conversation’, the communication platform with ‘Academic rigour & journalistic flair’. With the article, Ioannis, André and Gert try to answer the question whether science can help the endangered Cavendish banana to survive. The piece attracted very much interest of news media, it even reached the homepage of CNN.

Check the CNN page here:
http://edition.cnn.com/2016/10/25/health/banana-extinction/index.html

You can read the entire article here on The Conversation:
https://theconversation.com/with-the-familiar-cavendish-banana-in-danger-can-science-help-it-survive-64206

The Conversation is an independent source of news and views, sourced from the academic and research community and delivered direct to the public. Their team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.

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