Horticulture Group Newsletter - February 2012

Bananas unzipped

We are all familiar with the banana, either as the fruit found in our fruit bowls and sandwich boxes or as an ornamental plant whose large leaves give a 'tropical' accent to summer displays. However, it may come as a surprise to learn that, on a global scale, more bananas are eaten than any other fruit and it is the fourth most important staple food in the world. India leads the way in banana production followed by Brazil and China. However, these countries consume most of the crop that they produce so UK bananas are more likely to come from Ecuador, the world's largest exporter, Costa Rica or Guatemala. Some also come from Caribbean islands such as St Lucia where the banana accounts for around half the country's export earnings.

There are two basic types of banana; the familiar sweet type that we consume and the starchy 'plantain' that forms the staple in many tropical diets. However a visit to the banana collection at the Honduras Foundation for Agricultural Research (FHIA) at La Lima in Honduras soon makes you realise that there are a large number of other types of banana that we never see in the UK - different in size, shape, colour and sweetness.

The yellow seedless fruit we are used to is a 'Cavendish' banana, currently the most widely grown group of varieties. Seedless, yes, so how is it grown and how are new varieties produced? Almost all modern edible bananas come from the two wild species - Musa acuminata and Musa balbisiana from south east Asia. Cavendish bananas are all triploid forms of M. acuminata, in other words they have three sets of chromosomes instead of the usual two (diploid). This triploid status allows cell division (mitosis) to occur normally enabling the plants to grow and flower.

However, the extra set of chromosomes makes the meiotic division, necessary for the production of pollen and seeds, unstable and it almost always fails, so seeds are only very rarely produced. In most cases the absence of seeds would also cause the fruit to abort but fortunately the banana, like the slicing cucumber, is able to produce normal fruit even in the absence of pollination. Since it is impossible to hybridise triploid bananas, breeders have had to work with seeded diploid bananas and then recreate the seedless triploid forms.

The banana is the largest herbaceous plant in the world and grows from a corm. The plants like deep well-drained soil but plenty of water so are usually grown in regions of high rainfall. Each corm produces a single stem which ultimately produces a single pendant inflorescence. This consists of a number of 'tiers' or 'hands', each hand containing around twenty fruit and growing from the axil of a large purple bract.

Once a corm and its stem have flowered it dies and growth continues from daughter corms budded from the side of the parent. In commercial plantations only one such daughter is allowed to grow per plant to produce the next crop. Each one takes 6-8 months to produce fruit, and so the cycle of new corm, growth, flowering and death continues for 25 years or more in a commercial plantation.

This continuous long term vegetative propagation means there is very little genetic diversity in banana cultivars and makes it susceptible to pests and diseases some of which have proved as devastating as phylloxera (Daktulosphaira vitifoliae) was in 19th century French vineyards. In the early part of the 20th century the main variety was 'Gros Michel'. This cultivar eventually succumbed to Panama disease, a root rot caused by a race of Fusarium Oxysporium. Starting in the 1920s, and purportedly inspiring the song Yes we have no Bananas, this disease eventually wiped out all Gros Michel plantations and led to their replacement with Cavendish in the 1960s. Now a new race of F. oxysporium is gradually devastating Cavendish plantations so a replacement is needed.

Another major disease is Black Sigatoka, a leaf spot caused by Mycosphaerella fijiensi. Originally from Fiji this disease has spread around the world. It is being followed by Banana Xanthomonas Wilt (BXW) caused by Xanthomonas campestris. The spread of these diseases has created a major problem since the Cavendish banana could potentially be wiped out before breeders were able to create acceptable replacements by traditional means. One solution is genetic modification and lines resistant to Mycosphaerella and Xanthomonas as well as lines with improved nutritional characteristics have already been produced.

Plant of the Month

Ananas comosus, pineapple, Bromeliaceae

In the depths of the winter when it is cold and dark outside I like to sit and think of bright sunshine, warm seas and tropical plants. Visits to the Palm House at the Botanic Garden serve to transport me partially to such territories.

Amongst the many economically important plants growing in the Palm House is the pineapple. This plant is a member of the bromeliad family - a family of approximately 2400 species consisting of both epiphytic and terrestrial plants.

The pineapple plant itself surprises many people when they first see it growing. It forms a spiky rosette of leaves low to the ground from which arises a stem with a terminal inflorescence, which becomes the fruit familiar to us all. The fruit itself is a fleshy syncarp of 100-200 berry-like fruit. The fruit is topped with a tuft of leaves and this can be used to propagate a new plant.

Cut the top off the pineapple and remove most of the flesh. Leave the base of the tuft of leaves to dry out for a couple of days then pot into some good potting compost and place in a brightly lit, warm place (with some bottom heat if possible). New roots should form from the base of the rosette within a few weeks.

Pineapples first became known to Europeans when Columbus landed in Guadeloupe in 1493. They were then introduced to St Helena in 1505, the Philippines in 1558 and now are considered a weed in some countries.

In the early 1700s it became very fashionable to grow pineapples in the UK and they also became the model for lots of garden statuary - just look around you when visiting country houses. The pineapple pits at Heligan in Cornwall were restored in the 1990's and the growing of pineapples began there again.

The pineapple is still an important crop in many countries and regions today including Hawaii, with varieties such as Smooth Cayenne and Maui Gold. Pineapples are intrinsically linked with the post-contact history of these islands with early missionaries such as Dole becoming leading figures in commerce, then wielding their influence, leading to Hawaii ultimately becoming a US state.

Fibre from the leaves of this plant is strong and soft but difficult to extract. It can be made into beautiful, but expensive cloth. The fruit contains proteolytic papain-like enzymes - have you ever noticed the inside of your mouth feeling a bit funny after eating a lot of pineapple?

Although we call this fruit pineapple, many other languages including French, use the scientific name - Ananas which derives from the South American (Tupi) Indian name for the plant. The specific epithet - comosus - is actually very descriptive and means furnished with a tuft.

A tropical fruit that has influenced the course of history!

Alison Foster
Oxford Botanic Garden

Medicinal Plant of the Month

Carica papaya, papaya, pawpaw, Caricaceae

This tree is cultivated throughout the tropics for its edible fruit and for the enzyme papain. Papain (below) is a cysteine protease - it is an enzyme which breaks down proteins containing the amino acid cysteine. Papain is obtained from the papaya by scarifying unripe fruit. It has a multitude of uses. It can be bought in powdered form to be used as a meat tenderiser but is then also used as a home remedy for jellyfish, bee and wasp stings as well as for mosquito bites. It is suggested that it works by breaking down the protein toxins in the venom. It has also been used to reduce cloudiness in beer, to shrink-proof wool and silk and to control termites.

It also has some even more important medicinal uses. In hospital situations a gel called Accuzyme which contains papain is used to clean up dead tissue in chronic wounds. The technical term for papain is this situation is 'enzymatic debriding agent'. The enzyme breaks down the proteins in the dead tissue, allowing the by-products to be washed away - leaving the healthy flesh intact without any damaging physical cleaning.

Papain is also formulated into another product called Papcarie. This is again a gel and is used for chemomechanical dental caries removal.

The name Carica is of Latin origin and very similar to the Greek Karike which is a kind of fig. The name was transferred to papaya on account of its fig-like leaves.

Alison Foster
Oxford Botanic Garden

News from our Associates

Commercial Horticultural Association
After 15 years of running the UK exhibit at IPM in Hall 10, last year saw the CHA group expand to a second stand in the Technology Hall (3). This year IPM Essen saw the largest ever British presence over two large national pavilions in Hall 3 (Technology - stand 3B51) and 10 (Nursery - 10C13, 10C17). In the Technology Hall, the stands showcased a range of products and services from UK horticultural specialists including water soluble and liquid fertilisers, professional grower substrates, retail plant displays, specialist film-clad structures and a range of hydroponic and lighting equipment, growing media and propagation products.

Meanwhile in the nursery Hall British exhibitors included the world's leading breeder and propagator of English Pinks, an internationally recognised English rose breeder, a specialist micropropagation company and one of the largest specialist clematis nurseries in the world. For the first time a world leading soft fruit nursery exhibited, and they were joined on the UK Pavilion by the manufacturer of a specialist root control system.

Society of Biology
The Society is advertising for applicants for its Travelling Fellowships. Valued at £500, these are awarded to student and certain Associate members of the Society with the aim of offering the opportunity of overseas travel in connection with biological study, teaching or research to those who would otherwise be unlikely to have it. Applications must be received by 29 February 2012.

Horticulture Industry News

For the very latest horticultural news follow us on Facebook and or Twitter.

River levels could drop by 80%
Britain's rivers are drying up and unless emergency measures are adopted, some of our finest waterways could be reduced to trickles over the next few decades. This is the stark warning of an Environment Agency study into the predicted impact of climate change on the flow of rivers in England and Wales by 2050. In some cases, the agency warns, river levels in summer could drop by 80%. More

How to tell policymakers about scientific uncertainty
Uncertainty is intrinsic to science. Not all questions can be answered with 100 per cent certainty and even widely accepted theories can be challenged by new evidence. Policy makers and the public expect certainty and lobby groups capitalise on this. Being able to communicate the level of uncertainty in information scientists present to policymakers is crucial. Make uncertainty understandable. More

Colombian flowers market to expand towards Asia
Colombia is the second biggest exporter of cut flowers after the Netherlands, but 2011 was a difficult year for its flower growers. Experts blame not just economic problems in two of its main markets, United States and Europe, but also heavy rains and strong local currency. Now Colombian producers say it is time to look towards Asia. More

Spanish horticulture restructures
Greenhouse production of vegetables in southern Spain is suffering a deep crisis. Organisations involved in different activities, vegetable growers, research, credit, input suppliers, all are involved, like it or not, in deep restructuring. Some are joining forces to survive, others going into liquidation.

BASF stops GM production in Europe
Chemicals company BASF has announced it will stop developing and marketing genetically modified crops in Europe. The company will focus instead on markets in the US, Latin America and in Asia, where political and consumer resistance to GM crops is weaker than in Europe, BASF said in a statement on 16 January. 'We are convinced that plant biotechnology is a key technology for the 21st century.

However, there is still a lack of acceptance for this technology in many parts of Europe - from the majority of consumers, farmers and politicians,' said Stefan Marcinowski, a member of BASF's board of executive directors, responsible for plant biotechnology. 'Therefore, it does not make business sense to continue investing in products exclusively for cultivation in this market,' added Marcinowski.

Strathclyde University scientists end marabu weed nightmare
Once an innocent and attractive import from Africa, Marabou likes the fertile soil of Cuba rather too much. The decline of the Cuban sugar industry left thousands of hectares of land open to weeds and Marabu was quick to take advantage covering 1.7 million hectares of once-productive land. Now Strathclyde University's engineering faculty have found that they can produced high-quality activated carbon from it for a fraction of the cost of similar materials. More . Cuban researchers are also looking into using it for power generation. More

Methionine effective against citrus pests
University of Florida researchers have discovered a key amino acid essential for human nutrition is also an effective insecticide against caterpillars that threaten the citrus industry. The Lime Swallowtail, or Citrus Swallowtail, Princeps demoleus is a well-known agricultural pest from southern Asia discovered in the Caribbean in 2006. If not controlled, the caterpillars can completely defoliate young wild lime plants.

Experiments show that when methionine is sprayed on leaves it is 100 percent effective in killing larvae related to the Lime Swallowtail caterpillars within two to three days. Methionine's effectiveness is based on the biochemistry of the insect gut, so although this work was done on a surrogate, the methionine will block the ion channel of the Citrus Swallowtail in the same way. More

Açai pulp demonstrates neuroprotective effects in new mouse study
The pulp of the Açai palm, Euterpe oleracea, has been shown to have potentially neuro-protective properties in a study on mouse brain cells, suggesting pulp from the Amazonian fruit could combat some of the inflammatory and oxidative mediators of ageing at the cellular level. More

New tool puts plant hormone under surveillance
A team of scientists from France, UK and Belgium have developed a sensor that allows auxin to be visualised in plant tissues for the very first time. Called DII-VENUS, the new sensor can monitor rapid changes in auxin and allows researchers to visualise almost in real-time the redistribution of auxin during developmental responses. This has revealed much more complex patterns of auxin in tissues than previously thought, indicating that sensitivity to the hormone within tissues precisely control their capacity to respond.

China seeks to unlock secrets of herbs, roots
Chinese legends have long extolled the benefits of the Tian Shan Xue Lian or the Snow Lotus, Saussurea involucrata, a rare white flower found in snowcapped mountains that is revered as a panacea, an elixir so powerful it can supposedly bring the dead back to life. Chinese scientists have now extracted its key ingredient, acacetin, created its synthetic twin and found success in experiments on dogs with atrial fibrillation. They are now refining the compound and hope to begin human trials in three years.

Mycorrhiza and Salt Tolerance of Trees
Three years of nursery and field experiments with trees under practical conditions have shown the feasibility of using mycorrhizal fungi to improve the performance of trees in saline or salt-polluted soils. In particular ectomycorrhizal fungi seem to efficiently protect their host tree against salt stress. They showed that improved mycorrhization increased the salt tolerance of the sensitive tree species Tilia cordata and Fagus sylvatica to the level of salt tolerant tree species.

'Nourishing gene' brings hope for increased crop seed yield
Scientists have discovered a 'nourishing gene' which controls the transfer of nutrients from plant to seed. They identified for the first time a gene, named Meg1, which regulates the optimum amount of nutrients flowing from mother to offspring in maize plants.

Unusually only the Meg1 allele inherited from the female parent is expressed. The allele inherited from the pollen parent is switched off by a process known as imprinting. The findings mean that scientists can now focus on using the gene and understanding the mechanism by which it is expressed to increase seed size and productivity in major crop plants.

Chlorophyll can help prevent cancer
A recent study has found that the chlorophyll in green vegetables offers protection against cancer when tested against the modest carcinogen exposure levels most likely to be found in the environment. However, chlorophyll actually increases the number of tumours at very high carcinogen exposure levels. This casts doubt on the value of an approach often used in studying cancer-causing compounds where laboratory animals are exposed to a compound at high levels and then used to predict that a proportional amount of that same result would be present at low levels of exposure. More

Plant Tweets; 'Thanks for watering me'
We are used to receiving Tweets from humans but now plants can join the Twitter community. The device is called Botanicalls and when your plant needs water, it will post an update to Twitter letting you know that it is thirsty. It will even tweet a thankyou message after you water it.

Plant uses buried leaves to catch nematodes
Philcoxia minensis, a land based relative of the aquatic carnivorous Bladderwort (Utricularia) found in the UK, is the first carnivorous plant discovered to trap and devour prey in the soil with the help of sticky leaves prodded below the surface. Earlier investigations had shown that P. minensis's tiny subterranean leaves, each just 1.5 millimetres wide, were covered with grains of sand and the corpses of nematode worms. Now scientist have proof that the plants qualify as carnivores by digesting the nematodes. More

Marks & Spencer absorbs ethylene for 'longer-living' fruit
M&S becomes the first major retailer to roll out new packaging which it claims will extend the life of fruit stored in the fridge by up to two days. The supermarket will add a small plaster-style strip at the bottom of punnets of strawberries, containing a patented mixture of clay and other minerals that absorb ethylene - the gas which causes fruit to ripen. The strip measures 8cm x 4.5cm and does not affect the recyclability of the packaging. If successful, it will be added to all the supermarkets' berries. More

Soil microbiologists discover Aberdeen microbe of global agricultural significance
Scientists at the University of Aberdeen have filled a gap in our understanding of how ammonia-based fertilisers are inactivated by microorganisms in soil. Organisms that oxidise ammonia were first discovered in 1890. However, all the strains cultivated have only grown at neutral or higher pH, and not in acidic conditions. As 50% of the world's agricultural soils are acidic, the mechanism by which loss of fertiliser occurs in these soils has remained a mystery. Now research at the University of Aberdeen has identified a novel organism, named Nitrosotalea devanaterra, which performs the process of ammonia oxidation in acidic conditions, and has also demonstrated that this organism is abundant and globally distributed in acidic soils. More

Plants Keeping Time to Defend Against Attacks
Researchers have demonstrated that plant cells activate defences not only in response to pests, but in anticipation of them. With the help of internal clocks, the plants do so at a precise time each day. Knowing that plants are able to time their defences can inform scientists and farmers about when plants are most vulnerable to disease attacks. It could also help agriculturalists make efficient use of costly pesticides - applying them when plants need them the most.

These research findings also may be a clue that circadian clocks control immune defenses. Living organisms contain built-in biological clocks - also known as circadian clocks - that regulate the pattern of functions such as sleep or the opening of flowers. This is the first time scientists have identified a plant defence timed to a circadian clock. The plants trigger the defence mechanism at dawn, precisely when certain pests produce infectious spores.

Scientists made the connection when they mutated the plants' internal-clock genes and disrupted the defence mechanism. Each year, strange pest organisms called oomycetes inflict tremendous damage on agricultural, garden and forest plants. Oomycetes resemble fungi, but are actually distantly related to marine algae. Their unique biology makes them difficult to control with pesticides, so scientists are investigating the genes that control defence to learn more about strengthening plant immunity.

Herbal drug reduces the effects of alcohol
Alcohol consumption can lead to those dreaded hangovers and even alcohol dependence. However, a new study published in the Journal of Neuroscience has found a natural ingredient in the Asian tree Hovenia dulcis that seems to produce anti-alcohol effects. The main ingredient in Hovenia dulcis is known as dihydromyricetin, or DHM.

Using rats which react similarly to humans when it comes to the effects of alcohol, scientists showed that 'drunk' rats recovered faster and showed fewer signs of hangover symptoms such as anxiety and seizures when given DHM at the same time as alcohol. While these results will not lead to a magic pill that will allow you to drink and not face consequences, the results do hold some promise when it comes to the treatment of alcohol addiction. More

Dried licorice root fights the bacteria that cause tooth decay and gum disease
Scientists are reporting identification of two substances in the roots of the licorice plant, Glycyrrhiza glabra, that kill the major bacteria responsible for tooth decay and gum disease. They found that compounds, licoricidin and licorisoflavan A killed two of the major bacteria responsible for dental cavities and two of the bacteria that promote gum disease. Licoricidin also killed a third gum disease bacterium. The researchers say that these substances could treat or even prevent oral infections. More

Events Calendar

Other Events of Interest

Fruit Logistica
8 - 10 Feb, Messe Berlin
Berlin, Germany

The Gardens of Singapore
9 Feb, Oxford Botanic Garden
Oxford, UK

Bacterial Diseases of Stone Fruits and Nuts
14 - 17 Feb, International Society for Horticultural Science
Zurich, Switzerland

Early spring flowering perennials
16 Feb, Bristol Botanic Garden
Bristol, UK

International Strawberry Symposium
18 - 22 Feb, International Society for Horticultural Science
Beijing, China

Salon du Vegetal
21 - 23 Feb, Bureau Horticole Régional des Pays de la Loire
Angers, France

Quality Management in Postharvest Systems
21 - 24 Feb, International Society for Horticultural Science
Bangkok, Thailand

Quality Management in Supply Chains of Ornamentals
21 - 24 Jan, International Society for Horticultural Science
Bangkok, Thailand

Postharvest Pest and Disease Management in Exporting
21 - 24 Feb, International Society for Horticultural Science
Bangkok, Thailand

Postharvest Quality Management of Root and Tuber Crops
21 - 24 Feb, International Society for Horticultural Science
Bangkok, Thailand

Gardening is happiness-window boxes to the president of the RHS
23 Feb, Oxford Botanic Garden
Oxford, UK

Grower of the Year Awards
23 Feb, Haymarket Media
London, UK

World Food Technology and Innovation Forum
29 Feb - 1 Mar, World Trade Group
Dublin, Ireland

The Royal Garden Academy in Berlin: The revival of German horticulture
8 Mar, Oxford Botanic Garden
Oxford, UK

Hortec, Kenya
POSTPONED, ECO
Nairobi, Kenya

Flora of the Avon Gorge
15 Mar, Bristol Botanic Garden
Bristol, UK

The Landscape Show
15 - 17 Mar
London, UK

International Congress on Hazelnut
19 - 22 Mar, Instituto de Investigaciones Agropecuarias
Temuco, Chile

Flowers & Hortec Poland
20 - 22 Mar, BTO Exhibitions
Warsaw, Poland

International Flower Trade Expo
21 - 23 Mar, HPP Exhibitions
Nairobi, Kenya

Meadows at the Olympic park: elysium in the east end?
22 Mar, Oxford Botanic Garden
Oxford, UK

Medicinal and Aromatic Plants
22 - 24 Mar, International Society for Horticultural Science
Djerba, Tunisia

Biotechnology of Fruit Species
25 - 29 Mar, International Society for Horticultural Science
Nelson, New Zealand

Hunting for sustainability: ecology, economics and society
26 - 28 Mar, Instituto de Investigación en Recursos Cinegéticos
Ciudad Real, Spain

Crop World North America
27 - 28 Mar,
Charlotte, USA

IPM on the World Stage-Solutions for Global Pest Challenges
27 - 29 Mar,
Memphis, USA

New Ag International Conference & Exhibition
28 - 30 Mar
Bangkok, Thailand

Advances in Plant Virology
28 - 30 Mar, Association of Applied Biologists
Dublin, Ireland

Flower Bulbs and Herbaceous Perennials
28 Mar - 1 Apr, International Society for Horticultural Science
Antalya, Turkey

Mechanical Harvesting & Handling Systems of Fruits and Nuts
2 - 4 Apr, International Society for Horticultural Science
Lake Alfred, USA

Valuing Ecosystems: policy, economic and management interactions
3 Apr - 4 Apr, James Hutton Institute
Edinburgh, UK

Symposium on Artichoke, Cardoon and their wild relatives
10 - 13 Apr, International Society for Horticultural Science
Viterbo, Italy

Effective application: exploring synergy between Agricultural Economics and Applied Biology
16 - 18 Apr, Association of Applied Biologists
Warwick, UK

Registration of Agrochemicals
17 - 18 Apr,
Brussels, Belgium

Valuing Trees & Woodlands - a new understanding of their true worth
23 Apr, Institute of Chartered Foresters
Stoneleigh, UK

Symposium on Guava and Other Myrtaceae
23 - 25 April, International Society for Horticultural Science
Petrolina, Brazil

Protea Research Symposium
23 - 26 Apr, International Protea Association and International Society for Horticultural Science
Santiago, Chile

Insect Decline; The causes and the Role of Agriculture in Mitigation
25 Apr, SCI and Association of Applied Biologists
Harpenden, UK

History Comes to Life: Seventeenth-Century Natural History, Medicine and the 'New Science'
27 Apr, Society of Biology
London, UK

Biotechnology and other Omics in Vegetable Science
29 Apr - 2 May, International Society for Horticultural Science
Antalya, Turkey

If you would like to advertise a forthcoming event please contact. charne.green@soci.org

Horticulture Group Contact Details

For submitting ideas or to volunteer to be part of a committee or a group, please contact:

Chairman - Peter Grimbly
Meetings Secretary - Alison Foster
Minutes Secretary - Margaret Waddy
Newsletter co-ordinator - Sue Grimbly scihortigroup@btinternet.com
Group Contact - Charne Green charne.green@soci.org T: +44 (0)20 7598 1594