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Plant Science for Global Challenges

Tag: food security (page 2 of 10)

Fighting Fusarium wilt to beat the bananapocalypse

Dr. Sarah Schmidt (@BananarootsBlog), Researcher and Science Communicator at The Sainsbury Laboratory Science. Sarah got hooked on both banana research and science writing when she joined a banana Fusarium wilt field trip in Indonesia as a Fusarium expert. She began blogging at https://bananaroots.wordpress.com and just filmed her first science video. She speaks at public events like the Pint of Science and Norwich Science Festival.

 

Every morning I slice a banana onto my breakfast cereal.

And I am not alone.

Every person in the UK eats, on average, 100 bananas per year.

Bananas are rich in fiber, vitamins, and minerals like potassium and magnesium. Their high carbohydrate and potassium content makes them a favorite snack for professional sports players; the sugar provides energy and the potassium protects the players from muscle fatigue. Every year, around 5000 kg of bananas are consumed by tennis players at Wimbledon.

But bananas are not only delicious snacks and handy energy kicks. For around 100 million people in Sub-Saharan Africa, bananas are staple crops vital for food security. Staple crops are those foods that constitute the dominant portion of a standard diet and supply the major daily calorie intake. In the UK, the staple crop is wheat. We eat wheat-based products for breakfast (toast, cereals), lunch (sandwich), and dinner (pasta, pizza, beer).

In Uganda, bananas are staple crops. Every Ugandan eats 240 kg bananas per year. That is around 7–8 bananas per day. Ugandans do not only eat the sweet dessert banana that we know; in the East African countries such as Kenya, Burundi, Rwanda, and Uganda, the East African Highland banana, called Matooke, is the preferred banana for cooking. Highland bananas are large and starchy, and are harvested green. They can be cooked, fried, boiled, or even brewed into beer, so have very similar uses wheat in the UK.

In West Africa and many Middle and South American countries, another cooking banana, the plantain, is cooked and fried as a staple crop.

In terms of production, the sweet dessert banana we buy in supermarkets is still the most popular. This banana variety is called Cavendish and makes up 47% of the world’s banana production, followed by Highland bananas (24%) and plantains (17%). Last year, I visited Uganda and I managed to combine the top three banana cultivars in one dish: cooked and mashed Matooke, a fried plantain and a local sweet dessert banana!

 

Three types of banana in a single dish in Uganda.

Another important banana cultivar is the sweet dessert banana cultivar Gros Michel, which constitutes 12% of the global production. Gros Michel used to be the most popular banana cultivar worldwide until an epidemic of Fusarium wilt disease devastated the banana export plantations in the so-called “banana republics” in Middle America (Panama, Honduras, Guatemala, Costa Rica) in the 1950s.

Fusarium wilt disease is caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (FOC). The fungus infects the roots of the banana plants and grows up through the water-conducting, vascular system of the plant. Eventually, this blocks the water transport of the plant and the banana plants start wilting before they can set fruits.

Fusarium Wilt symptoms

Fusarium Wilt symptoms

The Fusarium wilt epidemic in Middle America marked the rise of the Cavendish, the only cultivar that could be grown on soils infested with FOC. The fact that they are also the highest yielding banana cultivar quickly made Cavendish the most popular banana variety, both for export and for local consumption.

Currently, Fusarium wilt is once again the biggest threat to worldwide banana production. In the 1990s, a new race of Fusarium wilt – called Tropical Race 4 (TR4) – occurred in Cavendish plantations in Indonesia and Malaysia. Since then, TR4 has spread to the neighboring countries (Taiwan, the Philippines, China, and Australia), but also to distant locations such as Pakistan, Oman, Jordan, and Mozambique.

Current presence of Fusarium wilt Tropical Race 4. Affected countries are colored in red.

In Mozambique, the losses incurred by TR4 amounted to USD 7.5 million within just two years. Other countries suffer even more; TR4 causes annual economic losses of around USD 14 million in Malaysia, USD 121 million in Indonesia, and in Taiwan the annual losses amount to a whopping USD 253 million.

TR4 is not only diminishing harvests. It also raises the price of production, because producers have to implement expensive preventative measures and treatments of affected plantations. These preventive measures and treatments are part of the discussion at The World Banana Forum (WBF). The WBF is a permanent platform for all stakeholders of the banana supply chain, and is housed by the United Nation’s Food and Agricultural Organization (FAO). In December 2013, the WBF created a special taskforce to deal with the threat posed by TR4.

Despite its massive impact on banana production, we know very little about the pathogen that is causing Fusarium wilt disease. We don’t know how it spreads, why the new TR4 is so aggressive, or how we can stop it.

Fusarium Wilt symptom

Fusarium Wilt symptoms in the discolored banana corm.

Breeding bananas is incredibly tedious, because edible cultivars are sterile and do not produce seeds. I am therefore exploring other ways to engineer resistance in banana against Fusarium wilt. As a scientist in the 2Blades group at The Sainsbury Laboratory, I am investigating how we can transfer resistance genes from other crop species into banana and, more recently, I have been investigating bacteria that are able to inhibit the growth and sporulation of F. oxysporum. These biologicals would be a fast and cost-effective way of preventing or even curing Fusarium wilt disease.

 

Twitter:           @BananarootsBlog

Email:              mailto:sarah.schmidt@tsl.ac.uk

Website:          https://bananaroots.wordpress.com

Brazil’s transgenic sugarcane stirs up controversy

By Luisa Massarani

This article was originally published on SciDev.Net. Read the original article.

[RIO DE JANEIRO] A genetically modified (GM) cane variety that can kill the sugarcane borer (Diatraea saccharalis) has been approved in Brazil,  to the delight of some scientists and the dismay of others, who say it may threaten Brazilian biodiversity.

Brazil is the second country, after Indonesia, to approve the commercial cultivation of GM sugarcane. The approval was announced by the Brazilian National Biosafety Technical Commission (CTNBio) on June 8.

Sugarcane borer is one of the main pests of the sugarcane fields of South-Central Brazil, causing losses of approximately US$1.5 billion per year.

“Breeding programmes could not produce plants resistant to this pest, and the existing chemical controls are both not effective and severely damaging to the environment,” says Adriana Hemerly, a professor at the Federal University of Rio de Janeiro, in an interview with SciDev.Net.

“Studies conducted outside Brazil prove that protein from genetically modified organisms harms non-target insects, soil fauna and microorganisms.”

Rogério Magalhães

“Therefore, the [GM variety] is a biotechnological tool that helps solve a problem that other technologies could not, and its commercial application will certainly have a positive impact on the productivity of sugarcane in the country.”

Jesus Aparecido Ferro, a member of CTNBio and professor at the Paulista Júlio de Mesquita Filho State University, believes the move followed a thorough debate that began in December 2015 — that was when the Canavieira Technology Center (Sugarcane Research Center) asked for approval to commercially cultivate the GM sugarcane variety.

“The data does not provide evidence that the cane variety has a potential to harm the environment or human or animal health,” Ferro told SciDev.Net.

To develop the variety, scientists inserted the gene for a toxin [Cry] from the bacterium Bacillus thuringiensis (Bt) into the sugarcane genome, so it could produce its own insecticide against some insects’ larvae.

This is a technology that “has been in use for 20 years and is very safe”, says Aníbal Eugênio Vercesi, another member of the CTNBio, and a professor at the State University of Campinas.

But Valério De Patta Pillar, also a member of the CTNBio and a professor at the Federal University of Rio Grande do Sul, points to deficiencies in environmental risk assessment studies for the GM variety — and the absence of assessments of how consuming it might affect humans and animals.

According to Pillar, there is a lack of data about the frequency with which it breeds with wild varieties. Data is also missing on issues such as the techniques used to create the GM variety and the effects of its widespread use.

Rogério Magalhães, an environmental analyst at Brazil’s Ministry of the Environment, also expressed concern about the approval of the commercial transgenic cane.

“I understand that studies related to the impacts that genetically modified sugarcane might have on Brazilian biodiversity were not done by the company that owns the technology,” said Magalhães in an interview with SciDev.Net. This is very important because Brazil’s climate, species, and soils differ from locations where studies might have taken place, he explained.

Among the risks that Magalhães identified is contamination of the GM variety’s wild relatives. “The wild relative, when contaminated with transgenic sugarcane, will have a competitive advantage over other uncontaminated individuals, as it will exhibit resistance to insect-plague that others will not have,” he explained.

Another risk that Magalhães warns about is damage to biodiversity. “Studies conducted outside Brazil prove that Cry protein from genetically modified organisms harms non-target insects, soil fauna and microorganisms.”

Magalhães added that some pests have already developed resistance to the Bt Cry protein, prompting farmers to apply agrochemicals that are harmful to the environment and human health.

This piece was originally published by SciDev.Net’s Latin America and Caribbean desk.

 

This article was originally published on SciDev.Net. Read the original article.

Rise in groundwater overuse could hit food prices

By Neena Bhandari

[SYDNEY] The increasing use of groundwater for irrigation poses a major threat to global food security and could lead to unaffordable prices of staple foods. From 2000 to 2010, the amount of non-renewable groundwater used for irrigation increased by a quarter, according to an article published in Nature on March 30. During the same period China had doubled its groundwater use.

The article finds that 11 per cent of groundwater extraction for irrigation is linked to agricultural trade.

“In some regions, for example in Central California or North-West India, there is not enough precipitation or surface water available to grow crops like maize or rice and so farmers also use water from the underground to irrigate,” the article says.

“When a country imports US maize grown with this non-renewable water, it virtually imports non-renewable groundwater.”

Carole Dalin,  Institute for Sustainable Resources at University College, London

The article focused on cases where underground reservoirs or aquifers, are overused. “When a country imports US maize grown with this non-renewable water, it virtually imports non-renewable groundwater,” Carole Dalin, lead author and senior research fellow at the Institute for Sustainable Resources at University College, London, tells SciDev.Net.

Crops such as rice, wheat, cotton, maize, sugar crops and soybeans are most reliant on this unsustainable water use, according to the article. It lists countries in the Middle East and North Africa as well as China, India, Mexico, Pakistan and the US as most at risk.

“Pakistan and India have been locally most affected due to groundwater depletion and exporting agricultural products grown with non-sustainable groundwater. Iran is both exporting and importing and The Philippines is importing from Pakistan, which is non-sustainable. China is importing a lot from India. Japan and Indonesia are importing, mainly from the US,” says Yoshihide Wada, co-author of the report and deputy director of the International Institute for Applied Systems Analysis’s Water Programme, Laxenburg, Austria.

Agriculture is the leading user of groundwater, accounting for more than 80 to 90 per cent of withdrawals in irrigation-intense countries like India, Pakistan and Iran, according to the report.

The researchers say efforts to improve water use efficiency and develop monitoring and regulation need to be prioritised. Governments must invest in better irrigation infrastructure such as sprinkler irrigation and introduce new cultivar or crop rotation to help producers minimise water use.

Wada suggests creating awareness by putting water labels, along the lines of food labels, “showing how much water is used domestically and internationally in produce and whether these water amounts are from sustainable or non-sustainable sources”.

Andrew Western, professor of hydrology and water resources at the University of Melbourne’s School of Engineering, suggests enforceable water entitlement systems and caps on extraction. “In recent decades, water reform in Australia has led to water having a clear economic value made explicit by a water market. This has enabled shifts in water use to cope with short-term climate fluctuations and has also driven a trend of increasing water productivity,” he says.

This piece was produced by SciDev.Net’s Asia & Pacific desk.

 

This article was originally published on SciDev.Net. Read the original article.

Striga hermonthica – a beautiful but devastating plant…

This week’s post was written by Caroline Wood, a PhD candidate at the University of Sheffield.

When it comes to crop diseases, insects, viruses, and fungi may get the media limelight but in certain regions it is actually other plants which are a farmer’s greatest enemy. In sub-Saharan Africa, one weed in particular – Striga hermonthica – is an almost unstoppable scourge and one of the main limiting factors for food security.

Striga is a parasitic plant; it attaches to and feeds off a host plant. For most of us, parasitic plants are simply harmless curiosities. Over 4,000 plants are known to have adopted a parasitic mode of life, including the seasonal favorite mistletoe (a stem parasite of conifers) and Rafflesia arnoldii, nicknamed the “corpse flower” for its huge, smelly blooms. Although the latter produces the world’s largest flower, it has no true roots – only thread-like structures that infect tropical vines.

When parasitic plants infect food crops, they can turn very nasty indeed. Striga hermonthica is particularly notorious because it infects almost every cereal crop, including rice, maize, and sorghum. Striga is a hemiparasite, meaning that it mainly withdraws water from the host (parasitic plants can also be holoparasites, which withdraw both water and carbon sugars from the host). However, Striga also causes a severe stunting effect on the host crop (see Figure 1), reducing their  yield to practically nothing. Little wonder then, that the common name for Striga is ‘witchweed’.

Striga-infected sorghum

Figure 1: Striga-infected sorghum. Note the withered, shrunken appearance of the infected plants. Image credit: Joel Ransom.

 

Several features of the Striga lifecycle make it especially difficult to control. The seeds can remain dormant for decades and only germinate in response to signals produced by the host root (called strigolactones) (Figure 2). Once farmland becomes infested with Striga seed, it becomes virtually useless for crop production. Germination and attachment takes place underground, so the farmer can’t tell if the land is infected until the parasite sends up shoots (with ironically beautiful purple flowers). Some chemical treatments can be effective but these remain too expensive for the subsistence farmers who are mostly affected by the weed. Many resort to simply pulling the shoots out as they appear; a time-consuming and labor-intensive process. It is estimated that Striga spp. cause crop losses of around US $10 billion each year [1].

Certain crop cultivars and their wild relatives show natural resistance to Striga. Here at the University of Sheffield, our lab group (headed by Professor Julie Scholes) is working to identify resistance genes in rice and maize, with the eventual aim of breeding these into high-yielding cultivars. To do this, we grow the host plants in rhizotrons (root observation chambers) which allow us to observe the process of Striga attachment and infection (see Figure 3). Already this has been successful in identifying rice cultivars that have broad-spectrum resistance to Striga, and which are now being used by farmers across Africa.

 

Life cycle of Striga

Figure 2: Life cycle of Striga spp. A single plant produces up to 100,000 seeds, which can remain viable in the soil for 20 years. Following a warm, moist conditioning phase, parasite seeds become responsive to chemical cues produced by the roots of suitable hosts, which cause them to germinate and attach to the host root. The parasite then develops a haustorium: an absorptive organ which penetrates the root and connects to the xylem vessels in the host’s vascular system. This fuels the development of the Striga shoots, which eventually emerge above ground and flower. Figure from [2].

 

But many fundamental aspects of the infection process remain almost a complete mystery, particularly how the parasite overcomes the host’s intrinsic defense systems. It is possible that Striga deliberately triggers certain host signaling pathways; a strategy used by other root pathogens such as the fungus Fusarium oxysporum. This is the focus of my project: to identify the key defense pathways that determine the level of host resistance to Striga. It would be very difficult to investigate this in crop plants, which typically have incredibly large genomes, so my model organism is Arabidopsis thaliana, the workhorse of the plant science world, whose genome has been fully sequenced and mapped. Arabidopsis cannot be infected by Striga hermonthica but it is susceptible to the related species, Striga gesnerioides, which normally infects cowpea.  I am currently working through a range of different Arabidopsis mutants, each affected in a certain defense pathway, to test whether these have an altered resistance to the parasite.  Once I have an idea of which plant defense hormones may be involved (such as salicylic acid or jasmonic acid), I plant to test the expression of candidate genes to decipher what is happening at the molecular level.

Striga-infected Arabidopsis

Figure 3: One of my Arabidopsis plants growing in a rhizotron. Preconditioned Striga seeds were applied to the roots three weeks ago with a paintbrush. Those that successfully attached and infected the host have now developed into haustoria. The number of haustoria indicates the level of resistance in the host. Image credit: Caroline Wood.

 

It’s early days yet, but I am excited by the prospect of shedding light on how these devastating weeds are so effective in breaking into their hosts. Ultimately this could lead to new ways of ‘priming’ host plants so that they are armed and ready when Striga attacks. It’s an ambitious challenge, and one that will certainly keep me going for the remaining two years of my PhD!

 

You can follow my journey by reading my blog and keeping up with me on Twitter (@sciencedestiny).

 

References:

[1] Westwood, J. H. et al. (2010). The evolution of parasitism in plants. Trends in Plant Science, 15(4): 227-235.

[2] Scholes, J. D. and Press, M. C. (2008). Striga infestation of cereal crops – an unsolved problem in resource limited agriculture. Current Opinion in Plant Biology, 11(2): 180-186.

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