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Remembering the world's most famous banana scientist

Fri, 11 May 2012 07:10:00 +0000

I never met Norman Simmonds, on whom I recently did a page in Musapedia. He died six months before I joined INIBAP in July 2002. Prior to doing a page on him I was glad he had shared so much of his vast knowledge of bananas (I keep my copies of Bananas and The Evolution of the Bananas at arm’s length since they are the first things I check whenever I am looking for information on bananas, even though new data have since poked holes in some of his hypotheses, like his account of domestication). But having read what people said about him after his death, at 79, I now regret having narrowly missed the opportunity to pick his brains (he apparently remained active right until his last weeks). I can only imagine how intimidating it would have been. He is said to have refused an entry in Who’s Who because their letter to him was sloppily written.

One thing I would have liked to better understand are his views on banana breeding. In his final years, he expressed disappointment in the slow progress made in breeding bananas for the world’s poor. He felt, among other things, that too much emphasis was being put on plant pathology (“no one ever improved a crop by researching its diseases as a starting point”) and biotechnology, which he called ‘biotechery’. These developments were not in the roadmap he presented at a 1986 meeting on breeding strategies. His subsequent frustrations could be linked to the extent he, like many others, have underestimated the logistical difficulties of identifying, collecting, disseminating and evaluating existing banana cultivars, the first step towards “the effective exploitation of banana clones for the agricultural good”. Breeding “of an international character” was supposed to follow, with local programmes eventually developing. To be fair, he recognized that the chance of success, which he estimated as excellent, depended on the “free and unrestricted movement of genetic material”. It could be that when he said those words in the late 1980s, he didn’t fully appreciate how restricted the movement of genetic material would become.

Many of his commentaries and papers are behind paywalls or not online, but I plan to track down some of them. For example, in 1984 he wrote an article, Duplication of research: A good or a bad thing?, that enquires into the circumstances in which duplication of research might be beneficial. The abstract, which is online, points out that “there is a widespread belief among scientific administrators that ‘duplication’ of research is wasteful of resources and should be stopped. This might be true if research were ever truly duplicated, but it is not: programmes with similar titles and objectives are likely to take different routes and to attack problems in different styles, a fact that is generally recognized by working scientists. Duplication might, indeed, be positively beneficial, not only by developing potentially complementary styles of attack but also in providing some competitive spur.” Sounds interesting, especially in view of the changes going on in the CGIAR system.

Judging from the titles of pieces he wrote (Bandwagons I have known, Pie in the sky, Cocoa confusion) I like to believe that had he lived longer Simmonds would have taken up blogging. I would certainly have followed him, just as I take pleasure rummaging through his writings on bananas. I especially like it when he throws a different light on the plant I have learned to love, in great part thanks to him. Writing about the hazards of banana cultivation in a 1962 New Scientist article, he doesn't single out pests and pathogens as the greatest one, but wind. “Not only do the quite moderate winds that are seasonally common in many parts of the tropics cause great (though more or less insidious) damage, but a cyclone can devastate thousands of acres in a few minutes, laying the broken plants out in near rows along the line of the first great gusts. No one knows the total losses caused by wind, but they are probably equal to the losses caused by all the pathogens put together. The surprising thing about bananas is not that they are subject to damage by wind but that they ever stand up at all, when one considers the mechanical disadvantage inherent in the bearing of a great mass of fruits at the top of a tall, herbaceous stem.”

To commemorate the 10-year anniversary of Simmonds' death, I invite everyone who knew him personally, or has been influenced by him, to enrich the Musapedia page on this great scientist or to post a comment below.

Australia's plant protection initiative

Mon, 30 Apr 2012 15:38:00 +0000

A team of scientists led by Queensland Alliance for Agriculture and Food Innovation is spearheading a $6 million Banana Plant Protection Programme. Instead of fighting pests and pathogens after they have become a major problem, researchers aim to keep banana plants healthy through resistant varieties and improved plant-protection systems.

The power of consumers

Mon, 23 Apr 2012 09:44:00 +0000

A staff of Altroconsumo, an Italian consumer organisation, blogs about her visit to banana plantations in Ecuador, where she attended the Second Conference of the World Banana Forum.

The bumpy road to sustainability

Thu, 05 Apr 2012 10:28:00 +0000

Are large retailers replacing transnational banana producers as the new villains? While The Economist praises Chiquita’s efforts to promote social responsibility and sustainability, campaigners for fair and sustainable banana supply chains condemn big retailers for undermining the efforts of global brands by cutting costs and sourcing their bananas directly from producers.

With a little help from (functional) biodiversity

Tue, 03 Apr 2012 11:12:00 +0000

CIRAD scientists take on the challenge of restoring ecosystem services and meeting farmers’ needs.

Photo by Mathieu Rouard

The banana farmers of Guadeloupe and Martinique in the Caribbean are all too familiar with the perils of growing a crop as a monoculture. As is usually the case, pest numbers went up and pesticides were brought in to control them. The results have been a contaminated environment, increased production costs, as well as stagnant yields and revenues. In Guadeloupe, the surface area cultivated in banana shrank from 8,000 hectares in 1981 to 3,000 in 2006.

In the 1990s, a series of bans on pesticides used against weevils and nematodes initiated a search for more sustainable and less damaging alternatives for producing the export crop. Many of the innovations developed by scientists at the French agricultural research centre CIRAD are variations on well-known cultural practices, such as intercropping, improved hybrids, cover crops, clean planting material, crop rotations and fallows, that can be applied individually or in combination. For example, combining a crop rotation, or a fallow period, with the use of tissue-culture plantlets has proved especially successful in reducing the use of nematicides.

Planting a cover crop is usually done to control weeds or soil erosion, but it is also shaping up to be a useful addition to the toolkit of agro-ecological innovations for keeping soil-dwelling pests in check. The working hypothesis is that increasing the diversity of plant food resources will have a knock-on effect on the diversity and abundance of herbivorous species and of their predators. A more complex food web with more predators at the top will result in a better regulation of crop pests. That’s the theory. Its translation into practices that farmers will adopt, and benefit from, is somewhat more complicated.

For one thing, not any plant species will do, says Philippe Tixier, a CIRAD scientist using his knowledge of ecological processes to make agricultural systems more sustainable and resilient. He gives the example of cover crops that increase the abundance of predators which, instead of going for the crop pests, prey on other predators, a phenomenon known as intraguild predation. Another unwanted outcome is when the new resource is consumed by the pests themselves, resulting in more of them.

Testing the theory

To select cover crops for field evaluation, Tixier and his colleagues ran simulation models into which they fed parameters measured on 11 candidate species. The objective was to select species that competed with weeds, but not with the banana plant. The cover crop also needed to be tolerant to shade. The species that performed best in the virtual banana plantation were then planted in experimental plots at the CIRAD Rivière Lézarde Research Station in Martinique.

To test the impact on nematodes, banana were planted in a former plantation that had been left fallow for a year, long enough to considerably reduce the abundance of plant-parasitic nematodes. Four cover crop species were tested: Bahia grass (Paspalum notatum) and three legume species (Neonotonia wightii, Pueraria phaseolides and Stylosanthes guianensis). The other treatments were bare soil (plots in which herbicide was regularly applied), and spontaneous cover (plots in which the natural vegetation, a mix of grass species, was allowed to grow back). Data were collected two years later.

The abundance of nematodes (the plant-parasitic ones as well as the free-living ones that feed on bacteria, fungi and other organisms, including nematodes) was measured in each plot. The plots with a cover crop had, as expected, more predators than the bare soil ones, but the effect varied with the cover crop. The plots with a grass cover crop had less parasitic nematodes, but more root-hair feeders, bacterivores and fungivores, than the plots with a legume cover crop, as well as more omnivorous predators, although not as many carnivorous ones. The greater number of omnivores observed in these plots suggests that they were responsible for keeping the number of nematode pests down. Moreover, some of the legume cover crops probably turned out to be good hosts for some of the parasitic nematodes, namely P. phaseoloides for the spiral nematode Helicotylenchus multicinctus and S. guianensis for the root-knot nematodes Meloidogyne spp.

Photo by Philippe Tixier

Another set of experiments highlighted the role of the cover crop in supporting non-pest populations that act as alternative prey to predators of banana pests. The cover crop was Brachiaria decumbens (Signal grass) and the predator a fire ant, Solenopsis geminata, which feeds on the eggs of the banana weevil, Cosmopolites sordidus. Taking advantage of the fact that the cover crop and the banana use different photosynthetic pathways that produce different ratios of carbon isotopes in the plant, Tixier and his colleagues analysed the isotopic signature of the fire ants. The results from the plots with a cover crop suggest that the diet of the ants had changed to include prey that fed on the cover crop (a C4 plant), rather than the banana (a C3 plant). The scientists suspect that the main alternative prey was leafhoppers.

Leafhoppers produce honeydew that the ants collect, in return for which they protect the leafhoppers from natural enemies, such as parasitoids and predators. The carbohydrate-rich honeydew could be partly responsible for the higher numbers of S. geminata in the plots with a cover crop. Another way the cover crop might have helped the ants is by moderating variations in temperature and moisture at the soil surface, thus making their habitat more stable and hospitable.

Since the ants also prey on weevil eggs, Tixier wonders what would happen if after planting a cover crop that supports an increase in the number of fire ants, the cover crop were removed. Would the ants, deprived of one of their prey, go en masse for the weevil eggs? “We would like to test the idea to see whether managing the cover crop can improve control”, he says.

From the research station to farmers’ fields

The possibilities seem limitless, until they are tried out. But even if an agro-ecological innovation passes muster with scientists, it can still be rejected by farmers. This is why all innovations go through a validation phase with farmers after the research part is over. The process is managed by the technical institute (Institut technique tropical) set up by CIRAD to be the link between research and its applications. “This phase is very important”, says Tixier. “Some plants that we thought would make great cover crops were initially disliked. Farmers have different criteria. Their feedback is important to find solutions to the problems they face and to orient future research. They keep us grounded.”

One of the difficulties with practices that harness ecological processes is that they cannot be delivered in a package or summarized in a few recommendations. To help farmers select which cover crop to plant, the French national institute for agricultural research INRA developed an online expert system based on the data CIRAD scientists gathered on the plant species they analysed. Users tell the system which ecosystem service (e.g. soil fertility, erosion control, weed control, nematode control) they are looking for, along with a description of the plot and other information. The system, which currently handles two crops only, banana and yam, produces a list of species with the most effective ones first.

The results are limited to the plants for which the scientists have data, but even if the suggested species are not available in a given country, the information is still useful. People can narrow down the field by looking for local plants with similar functional traits. Agro-ecological knowledge may not be prescriptive, but it certainly is adaptable.

External links

SIMSERV, the expert system for the selection of cover (service) crops

Cover crops alter the soil nematode food web in banana agroecosystems in Soil Biology & Biochemistry

New primary resource increases predation on a pest in a banana agroecosystem in Agricultural and Forest Entomology

Landscape of the week

Mon, 02 Apr 2012 14:20:00 +0000

A blog on landscapes selected the Kuk Early Agricultural World Heritage Site as its landscape of the week. The site is one of the earliest known landscapes in the world where agriculture was practiced and the earliest evidence for the domestication of plants, including banana, in the Pacific region.

Matooke flour trailblazer

Mon, 02 Apr 2012 14:18:00 +0000

The East African has an article on one of Uganda’s most celebrated food technologists, Rev Dr Florence Muranga. The founding director of the Presidential Initiative on Banana Industrial Development is famous for turning matooke (banana) into shelf-stable flours, thus preventing millions of tonnes of the crop from going to waste.

Battling an invisible enemy

Wed, 28 Mar 2012 11:00:00 +0000

Different approaches to controlling nematodes without nematicides.

Plant-parasitic nematodes often go undiagnosed until a banana plant topples over, its roots eaten away by the minute roundworms, or until an expert in nematodes comes around, as nematologists sometimes say in jest. This is because most people don’t immediately think of nematodes when they see a plant growing more slowly, taking longer to fruit and producing a smaller bunch – typical symptoms of a moderate infection. The fact that nematodes are all but invisible also makes it difficult for farmers to notice them.

Adding to the problem is the practice of growing bananas in monocultures, which allows nematodes to proliferate. In commercial plantations nematodes are often controlled with nematicides. These products, however, are increasingly condemned because of their toxicity. Participants at the recent World Banana Forum Conference identified nematicides as one of the top three products impacting environmental and human health and called for a reduction in their use.

In the French West Indies, where carbamate and organophosphate nematicides have been gradually banned, the search for alternatives is well under way. One of the innovations developed by scientists from the French agricultural research centre CIRAD consists in replacing bananas with a non-host crop, or leaving the land fallow for a year or so, in order to eliminate the nematodes in the soil. To avoid reintroducing nematodes when bananas are replanted, farmers are advised to use pest- and disease-free plantlets produced through tissue culture (TC plantlets for short).

When the approach was first applied on the island of Martinique, the number of nematodes quickly built up after only one production cycle. The unexpected result was attributed to the mechanical method used to destroy the banana plants which, by leaving behind viable bits of rhizome, provided a safe haven for nematodes. Experiments led to the recommendation of injecting plants with glyphosate, a broad-spectrum systemic herbicide, and coming back to remove escapees and regenerated shoots. Even if the practice translates into more herbicide being used, the net result is still positive for the environment since glyphosate is far less toxic than nematicides and the doses used much smaller. Increases can also be offset by other practices that reduce herbicide use, such as planting a cover crop which, depending on the species, has also been shown to help keep nematodes in check.

“The crop rotation and TC plantlets system has made it possible for farmers to grow bananas for 3 to 5 years without having to use nematicides”, says Sébastien Zanoletti, Director of sustainable development at the Guadeloupe and Martinique banana producers union UGPBAN. Fourteen years after it was first introduced, the combination of a fallow, or crop rotation, and TC plantlets has led to a 90% reduction in the quantity of nematicides being used. Not all farmers, however, have adopted the cropping system.

A survey of 607 banana farmers indicates that in Guadeloupe 67% of farmers rotate bananas with another crop or a fallow period, and 59% use TC plantlets, compared to respectively 28% and 24% in Martinique. “The adoption rate tends to be lower in small farms”, says Jean-Marc Blazy of the French national institute for agricultural research INRA, “especially in Martinique. Lack of land is an obstacle, but the initial high investment is also an issue. Our simulations for a 4.2-hectare farm show a decline in revenues for the first two years and a half. After that transition period, however, revenues increase considerably compared to the pre-conversion level.” According to Blazy, farms in Guadeloupe are more diversified than in Martinique and farmers better informed about innovations. These factors may help explain why a larger proportion of farmers have adopted the practices.

Planting resistant varieties, either singly or in mixtures, is also an option, especially for smallholder farmers who cannot afford crop rotations or fallows. Experiments in Martinique have shown a reduction in the densities of nematodes following the introduction of the relatively resistant FB924 variety, an improved hybrid produced by CIRAD breeders, in a field of more susceptible Cavendish or plantain cultivars.

The GM way

GM bananas are not among the options proposed to the growers in the French West Indies, but in GM-friendly Uganda farmers may one day have access to cooking bananas genetically modified to be resistant to nematodes. Scientists at Uganda’s National Agricultural Research Organization and the International Institute of Tropical Agriculture are respectively transforming cultivars of East African highland banana and plantain, in collaboration with scientists at the University of Leeds, who supplied the gene constructs.

The strategy consists in introducing two genes with different modes of action to make it harder for nematodes to overcome the plant’s defence mechanisms. One of the genes codes for cystatin, a protein that by disrupting digestion essentially starves the nematodes, but only after the nematodes have started attacking the roots, since the cystatin needs to be ingested. The cystatin introduced in the plantain cultivar comes from maize, while the one in East African highland banana cultivar is derived from rice.

The other introduced gene codes for the production of a peptide, a short protein, that when secreted by the plant’s roots disorients nearby nematodes, preventing them from entering the roots. A fluorescent form of the peptide was used to reveal how it is taken up and transported to the nematode’s chemoreception cells, where it binds to nicotinic receptors.

In a greenhouse trial of 18 lines of the plantain cultivar Gonja manjaya, the GM plants that had the largest effect on nematode numbers, compared to their non-transgenic counterparts, were the ones that had the cystatin gene only. They reduced nematode numbers by 84%, compared to 66% for the plants that had the peptide gene only and 70% for the plants with both genes. The four best performing lines will be further evaluated in a confined field trial in Uganda later in the year, along with other transgenic lines of plantain and East African highland banana. Their performance will be compared to plants of the same cultivar that have been submitted to the same transformation process, but into which no new genetic material has been introduced.

The University of Leeds has donated its patents so farmers in developing countries would not have to pay extra for GM bananas. The question is more how will farmers access them. The delivery system will most likely rely heavily on TC plantlets, a system that is currently underdeveloped in East Africa, but should be in better shape by the time these nematode-resistant transgenic bananas become available.

The Pacific connection

Thu, 22 Mar 2012 09:30:00 +0000

Efforts to conserve Pacific bananas aim to raise awareness on their importance and shed light on their tangled history.

From diploids to triploids

In bananas, the first stirrings of edibility appear in plants which, like the wild species they are derived from, are diploid, meaning that they have two sets of chromosomes. These plants are parthenocarpic, that is they do not need pollen to trigger fruit development, but are still fertile. Evidence suggests that edible bananas went through a series of crosses that have left them increasingly sterile and seedless. Triploid bananas were produced when a male parent normally passed on a single chromosome set, while the female one contributed both sets, making further sexual reproduction even more unlikely and vegetative reproduction obligatory.

Botanists having established that the wild species Musa acuminata was one of the ancestors of bananas, Simmonds surmised that triploid bananas with acuminata-like traits (which he designated by the letters AAA) had been domesticated in Malaysia, where he said the species was at its most variable. It has since been shown that subspecies of acuminata not present in Malaysia were also implicated in the domestication of bananas. Since these subspecies occupy distinct geographic regions, such as the Philippines, Indonesia and New Guinea, plants must have been moved around in order to come into contact and hybridize. More difficult to pin point is where the diploid AAs came in contact with another wild species, Musa balbisiana, eventually giving rise to AB, AAB and ABB cultivars.

After his 1954 visit to what is now Papua New Guinea, Norman Simmonds, the author of seminal books on bananas, predicted that the area’s unusually high diversity of diploid bananas would soon be replaced by hardier and more productive triploid ones (see From diploids to triploids). His theory was that edible diploids had been introduced from southeast Asia early in the domestication process and owed their survival to the late arrival of triploid bananas.

Collecting missions conducted in 1988-89 did not bear out Simmonds’ prediction. The catalogue of material collected in PNG shows that, more than 30 years after his visit, edible diploids were still widespread, suggesting they were being actively conserved. Not only had they not disappeared, it also turned out that they had not been introduced either. It was eventually demonstrated that diploid, as well as triploid, bananas had been independently domesticated in the New Guinea area, along with the obviously local Fei bananas.

Meanwhile, accounts from the other side of the Pacific were mentioning groups of bananas designated Iholena, Maoli and Popoulu after the Hawaiian name of the most important cultivar in each group. Because the ancestors of the people who settled Polynesia are from southeast Asia, Simmonds believed that these ancient introductions were also from that part of the world. These Pacific plantains, as they came to be known, were eventually shown to also have originated in the New Guinea area.

Pacific plantains were not the only types of bananas introduced by Polynesian settlers. Fei bananas were also part of the voyage. For a while, it looked as if these once abundant fruit were irreversibly declining. In the early 2000s, however, reports of high levels of provitamin A carotenoids helped raise interest in their cultivation and conservation. A high-profile Go Local campaign in the Micronesian State of Pohnpei inspired other efforts to reduce dependence on imported foods by promoting and conserving local crops. For example, in the Solomon Islands the Kastom Gaden Association set up four banana collections with support from the Christensen Fund, while in Vanuatu, material collected on eight islands was planted in the Vanuatu Agricultural Research and Technical Centre's field station on the island of Santo.

A field collection for Pacific bananas

In French Polynesia, a field collection set up by the Ministry of Agriculture’s Maurice Wong has been selected as the host for the regional Pacific banana field collection funded by the Global Crop Diversity Trust. The field collection is working in partnership with the regional Pacific collection managed by the Secretariat of the Pacific Commission (SPC) in Fiji, which is conserving material received from member countries. The SPC maintains the plants in its care as tissue cultures and ensures that they are free of viruses before they are sent to French Polynesia. The regional collections are also linked with the international collection managed by Bioversity International at the International Transit Centre (ITC) in Belgium and are part of MusaNet.

The field collection in French Polynesia will focus on Pacific plantains and Fei bananas. Wong is pooling the plants he collected on six islands with material sent by the SPC. The plants will be characterized and evaluated for their agronomic performance. “The collection will also provide an opportunity for identifying duplicates and resolving taxonomic questions that should help target efforts to conserve the most representative diversity”, says Mary Taylor, the SPC Genetic Resources Coordinator. In the case of Pacific plantains, this will be facilitated by comparing the plants’ morphological characters with their genetic profile, which will be analysed by scientists at the Institut Agronomique néo-Calédonien and the French agricultural research centre CIRAD. “We’re hoping something similar will be done for the Fei bananas in the regional collection”, adds Taylor. “It would greatly increase our understanding of this little known group.”

Molecular markers have proved useful in exposing unexpected kinship. For example, they have shown that two important staples cultivated outside the banana’s primary centre of diversity, the African plantains and East African highland bananas, also trace part of their ancestry to the New Guinea area. The finding fits observations of PNG edible diploids exhibiting traits that anticipate these bananas.

Classifying the edible diploids will be a complicated undertaking, one of the reasons they are not currently included in the regional Pacific collection. Moreover, many of them are already in collections. The specimens collected during the 1988-89 collecting missions were planted at the PNG National Agricultural Research Institute’s field collection in Laloki and many of them have been duplicated at the ITC. Although they probably represent much of the diversity, it's unlikely that all the edible diploids were collected at the time, according to Jeff Daniells who participated in the missions. Unfortunately, when he went back to PNG in 2002, he noticed that introduced triploid varieties were more common in banana plantings. To stem the trend, he suggests enlisting farmers in what he calls community-based conservation sites. “The farmers”, he says, “could fund their conservation efforts from the sale of fruits and planting material and receive bonuses when they maintain or increase diversity in their plots”. Incentive schemes such as the payment for agrobiodiversity conservation services (PACS) being tested by Bioversity could be used to support the on-farm conservation of the less marketable cultivars.

Such a set up would help buy time to learn more about these bananas and find out why farmers have kept on growing them ... and maybe prevent Simmonds’ prediction from coming true.

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Reactions from the WBF

Tue, 20 Mar 2012 14:57:00 +0000

Fairfood International's representatives and Alistair Smith of BananaLink share their impressions of the second global conference World Banana Forum held at the end of February in Guayaquil, Ecuador.