Mar 15, 2018 | Publications
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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Nov 21, 2017 | Publications, Studies
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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Oct 30, 2016 | Publications, Publicity
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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Aug 20, 2016 | Publications
DNA of banana fungus unravelled for more sustainable banana crops. An international consortium led by Prof. Gert Kema from Wageningen University and Research has unravelled the DNA of Pseudocercospora fijiensis, the fungus that causes the dreadful black Sigatoka disease in bananas. The findings provide leads for increasing the sustainability of banana cultivation. For instance through the development of a resistant banana plant. The results were published in the scientific magazine PLoS Genetics.
Read more at: http://www.wur.nl/nl/nieuws/dna-banana-black-sigatoka.html
Read more at: http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005876
More information about Black Sigatoka
Black Sigatoka or black leaf streak disease, caused by the ascomycete fungus Pseudocercospora fijiensis, inflicts huge costs on banana producers, due to crop losses and expenses for disease control. The global banana export trade relies on Cavendish clones that are highly susceptible to P. fijiensis. Sustainable production of the world’s number one fruit requires a better understanding of host resistance and sophisticated management of fungicide resistance in the pathogen. In the P. fijiensis genome sequence we identified an effector that induced an HR-like necrosis on a resistant banana accession but not on a susceptible cultivar. If validated, this assay may be useful for identifying resistance in banana breeding programs. We also used the genomic sequence to develop highly polymorphic molecular markers for analyzing P. fijiensis field populations and identified a strong enrichment (nearly 100%) for fungicide resistance markers in fungicide-treated banana plantations compared to untreated wild-type populations. This rapid evolution of fungicide resistance poses an immediate threat to sustainable banana production.
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Apr 21, 2016 | Publications
Scientists at Wageningen UR have demonstrated that the same clone of the Fusarium fungus is infecting Cavendish bananas in several countries dotted across the globe. This shows that this Fusarium clone, also known as Tropical Race 4, is continuing to spread despite the quarantine measures, with disastrous results for banana growers. The results from the research appeared today in the scientific journal PLOS Pathogens.
Panama disease is caused by the Fusarium oxysporum f.sp. cubense fungus. One of the Fusarium strains is called ‘Tropical Race 4’ (TR4) and infects many local banana varieties as well as the widely exported Cavendish banana, which is very susceptible to this strain. The soil-borne fungus enters the banana plant through the root and eventually kills the entire plant. Banana-growing plots infested with the fungus remain contaminated for many years. It is then no longer possible to cultivate bananas on such a plot of land, as new banana plants become infected too. Large areas of banana plantations in countries such as Jordan, Mozambique, China, the Philippines, Pakistan and Australia are no longer suitable for banana farming, as they have become infested with the Panama disease fungus. There are currently no means of combating the disease; only quarantine measures can prevent banana plantations from becoming infested.
DNA investigation
The researchers at Wageningen UR analysed the DNA of many fungus specimens from eight countries where the fungus has recently been identified, including Jordan, Lebanon and Pakistan, in order to trace how Panama disease has come to spread to different locations across the globe. The research highlighted that the strains of the fungus, which were collected are genetically identical. The strains are clones. Gert Kema, banana expert at Wageningen UR, says: ‘This research demonstrates that the quarantine measures and information provided around the globe apparently have not had the desired effect.’
A tale of two clones
Not only the TR4 fungus strain is a clone: all Cavendish bananas also share the same genes. Kema explains: ‘The Cavendish banana is very susceptible to TR4. Therefore, the fungus can spread easily due to the worldwide monoculture of Cavendish bananas. That’s why we have to intensify awareness campaigns to reach small and large-scale growers in order to help them with developing and implementing quarantine measures preventing the fungus from continued spreading.’[/two_third]
Worldwide approach needed to stop further spreading
To stop further spreading, Kema’s team is working with a large number of partners in different locations across the globe to develop short-term solutions for Panama disease management. Kema continues: ‘We are gaining more and more insight into the scope of the issue. The ability to quickly identify infected banana plants and infested soils is extremely important in this respect. However, eventually we have to come up with long-term solutions, particularly host resistance, which can only be developed in strong multidisciplinary alliances with various partners and industry.’
The research was carried out by Wageningen UR in cooperation with the University of Queensland and Diversity Arrays Technology Pty Ltd in Australia and the University of Florida in the United States.
You can read the complete article in PLOS Pathogens via: http://dx.plos.org/10.1371/journal.ppat.1005197
Contact Gert Kema, banana expert at Wageningen UR, for questions about the research.
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Feb 11, 2016 | Publications
Corbana, the National banana corporation of Costa Rica, recently has published some Spanish documents that address the Tropical Race 4 issue. These aim to raise awareness of the recommendations that can help to prevent the rapid spreading of the disease.
“A serious treat for the global banana and other Musa species production in Costa Rica and the World” Click to view PDF
“Dear worker help us to keep our plantations free of panama disease” Click to view PDF
“Recommendations to prevent the introduction of quarantine diseases of high economic importance for banana and pineapple.” Click to view PDF
“Recommendations to prevent the introduction of FocTR4 in banana farms of Costa Rica” Click to view PDF
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