Publications

The Garden
November 2004

General news

Gardeners get closer to blight-resistant potatoes

Developments in breeding have led to the selection of two potato cultivars claimed to be the most blight resistant on the home market.

With the reduction in the number of pesticides available for garden pest and disease control, and a summer where blight has been widespread, this introduction is both welcome and timely.

One new cultivar is a red-skinned, maincrop called ‘Sarpo Mira’ from Thompson & Morgan and is one of a number of Sarpo cultivars bred by generations of the Sárvári family in Hungary, using potatoes collected from Mexico by Russian scientists during the 1920s.

Successful breeding has developed the natural resistance of these potatoes to the late blight fungus (Phytophthora infestans) and in trials the Sarpo cultivars showed high resistance in the foliage and tubers and outlived other cultivars with an innate resistance such as ‘Stirling’ and ‘Lady Balfour’.

At the University of Wales, David Shaw, Director of the Sárvári Research Trust, has trialled 20 Sarpo cultivars but other trials have been carried out in the last 15 years at numerous locations across the country including RHS Gardens Wisley, Rosemoor and Harlow Carr.

Tubers on trial

‘Sarpo Mira’ is the first potato to score full marks in commercial evaluations against blight and it is hoped that a second cultivar, ‘Sarpo Axona’, will be introduced in 2006. However this can only happen after it has been accepted on to the full National Listing, an approval process through which all new potato cultivars have to go before they can be released for sale.

Performance of ‘Sarpo Axona’ at RHS Garden Wisley was promising. Image: Mike Sleigh

A third cultivar, ‘Sarpo Tominia’, did not get National Listing because it was genetically too similar to ‘Sarpo Mira’. It therefore will not be introduced.

Chris Prior, RHS Head of Plant Pest and Disease Science, said performance of the three Sarpo cultivars at RHS Garden Wisley was initially promising but says the long-term stability of their blight resistance needs careful monitoring, because the late blight pathogen has a long history of overcoming resistance in potatoes.

The tubers from all three RHS gardens were lifted at the beginning of October.They were weighed and the foliage measured. Richard White from Wisley’s Model Vegetable Garden, where some plants were grown, observed that good, clean tubers had been produced with minimal slug damage and that, for the time of year, the plants showed a substantial amount of clean foliage. From five roots of ‘Sarpo Mira’, 73 tubers were produced weighing 8.4kg (18.5lb).

Global race

Gardeners are set to benefit from the hunt for potatoes with high resistance to blight because of their high commercial value. It is thought that direct losses to potato crops in developing countries costs more than US$3.25bn. It is impossible to estimate the figure for indirect losses, for example from lower yields or poorer quality.

Breeders across the world are working towards the same aim including the Cornell University in the USA which has recently sent 20 cultivars to Russia for trialling (where weather conditions make blight a huge problem) and Wisconsin-Madison University.

Chemical control

Current legislation still permits gardeners to use Bordeaux mixture and traditional copper fungicides as protectants for the control of late blight, but the use of copper in commercial pesticides is being reduced annually until withdrawal in 2008.

Products containing copper will be up for review on 31 Dec 2008 but according to DEFRA this could be brought forward if ‘earlier decisions are made or further prescribed extensions are granted’. Gardeners can also use products containing mancozeb. Both copper-based products and those containing mancozeb prevent the spores of late blight entering the leaf but do little to control the disease once established.

Worries over next generation of park workers

The Government is being called on to recognise the urgency of the crisis in green-space skills following a report suggesting that council parks departments are struggling in the face of a serious skills shortage.

The problem, it says, affects senior management downwards and occurs because there are too few young people being trained to take the place of staff reaching retirement. One of the reasons for this is the outcome of short-term savings from successive restructurings and Compulsory Competitive Tendering. It is estimated that over the last 20 years £1.3bn has been cut from spending on UK parks.

The report ‘Parks need people need parks’ commissioned by environmental and parks agencies including CABE Space (the Commission for Architecture and the Built Environment), the Countryside Agency and English Nature, states that 68 percent of the parks workforce are over the age of 40 and 60 percent have been in the same post for more than a decade.

CABE Space is also planning to lobby national policymakers with its Manifesto for Better Public Spaces. The Manifesto, which has the backing of the RHS, will be presented to Government ministers and experts at the Sustainable Communities Summit in January 2005 in Manchester. For information tel: 020 7960 2400, or visit: www.cabespace.org.uk.

Chinese magnolias red-listed as endangered

An assessment of the state of Chinese magnolias and their close relatives paints a gloomy picture for their future in the wild.

Around 30 species of Chinese Magnoliaceae are proposed for inclusion in the International Union for Conservation of Nature (IUCN) ‘Red List’ of plants and animals threatened with extinction, six in the highest category of risk (Critically Endangered) and 15 in the second highest (Endangered).

China (particularly Yunnan province) is rich in native magnolias and other Magnoliaceae, with some 160 species originating there. Professor Weibang Sun, magnolia expert from the Kunming Institute of Botany, explained: ‘Many species have declined dramatically in the wild as the pressure for agricultural land and firewood has destroyed or fragmented the forests in which they occur. Collection of bark or other parts for medicinal purposes and seeds for cultivation have also affected some species, and we are now facing the consequences.’

A workshop in June organised by IUCN Global Trees Specialist Group and Kunming Institute of Botany identified that among the Critically Endangered species are Manglietia sinica, known from 12 individuals and Magnolia zenii, with only 18 individuals in one wild population. Magnolia sargentiana, classified as Endangered, suffers from severe habitat fragmentation and just 40-50 mature trees are known from Yunnan province.

Manglietia decidua (above), a newly described species classified as Endangered, is known from about 500 individuals. Image: Professor Weibang Sun

Theft and destruction in wake of US hurricane

Hurricane Frances, which tore through parts of the USA this autumn, has left the garden of the America Orchid Society (AOS) in Florida severely damaged. The hurricane also led to the theft of more than 30 endangered cycads from the Fairchild Tropical Botanic Garden in southern Florida.

According to Executive Director of the AOS Lee S Cooke, one in four trees in its garden were either snapped in half, bent over or pulled out of the ground, and orchids growing in the branches had to be salvaged. After 24 hours of high winds and rains access to the gardens was limited, but staff were later quick to prune and stake trees that could be saved and clear those that were completely destroyed. Replacements for some of the lost trees are already
being sought.

At Fairchild the theft of cycads occurred because it was in one of the mandatory evacuation areas. Thieves entered the garden during the evacuation and took plants representing more than 20 species, many of which had been in the garden for decades and are irreplaceable. ‘As we worked to protect Fairchild’s staff and property from the effects of Hurricane Frances, the looters saw an opportunity to take some of our most valuable plants,’ says Director Mike Maunder.

Killer ladybirds threaten UK insects and plants

The future for British ladybirds and other beneficial insects could be under threat following the first UK sighting, in a pub garden in Essex, of what is being labelled the ‘killer ladybird’. Harmonia axyridis also known as the harlequin ladybird, was initially introduced in the United States for the purposes of biological control. It is now the most-common ladybird in the USA where its appetite for aphids and other ladybirds is devastating insect populations.

Harmonia axyridis is destructive to plants as well. Soft-fruit growers have reported damage to their fruits and vine growers say the ladybirds’ defensive chemicals taint the vintage.The first UK sighting was identified by Michael Majerus of the Genetics Department, University of Cambridge, who is
urging UK gardeners to keep on the alert for ladybirds in new locations.
For more information visit: www.rhs.org.uk/news/newladybird.asp

Sudden oak death: disease update

Experts from the USA, Europe and the UK will meet later this month to discuss the way forward in dealing with Phytophthora ramorum, often known as ‘sudden oak death’.

Ramorum dieback or ‘sudden oak death’ on Quercus falcata (American red oak)

The event comes as a Europe-wide risk assessment project is under way into the threat of the fungal pathogen and the discovery of a second species (with a working title of Phytopthora taxon C) which has been found in Cornwall causing similar damage to beech trees and rhododendrons.

Last year, the Department for Environment, Food and Rural Affairs (DEFRA) hosted a meeting to bring government and industry representatives together to address sudden oak death. The department is holding a follow-up meeting in London to discuss progress. This will focus on the current situation on outbreaks, as well as scientific understanding of the organism and its impact.

A recent search of 1,000 woodlands in Britain failed to find any further cases of the pathogen but studies by Forest Research suggest that other species such as Castanea sativa (sweet chestnut) and Fagus sylvatica (beech) may be highly susceptible.
For more information visit: www.defra.gov.uk/planth/ph.htm

New York garden for UK victims

Members of Parliament and the three main political parties in the UK have endorsed an appeal launched in September to raise £1 million for the British Memorial Garden in New York for the victims of the attack on the World Trade Center three years ago. More than 200 MPs signed a motion to support the garden that is to be built in Hanover Square, Manhattan, three blocks south of the World Trade Center site.

Designed by Julian and Isabel Bannerman it will feature paving from Scotland, a water rill of Welsh slate and curved benches of Portland stone. The planting scheme draws on traditional elements found in UK gardens and is based around clipped topiary, yew and boxwood hedges. The centrepiece will be a black granite block sculpture reaching 20ft (7m).

New trust set up in New Zealand

The New Zealand Gardens Trust has been set up by the Royal New Zealand Institute of Horticulture to promote excellence in the garden sector through the setting of standards and provision of educational opportunities. The trust also has plans to develop a relationship with Tourism New Zealand via its website (http://www.gardens.org.nz/). The site offers a database of gardens open to the public (which it has endorsed) so that garden visitors can create their own itineraries according to their garden interests.

French wine to help UK trees

English Oak and Sweet Chestnut are the names of two organic wines made in France the profits of which will go towards protecting ancient trees in the UK.

The venture between Robert Eden, owner of Comte Cathare vineyards in France, and the Woodland Trust means that 50p from every bottle sold will
help support major projects to protect and preserve some of the UK’s ancient trees.

Produced in the Languedoc region of France, English Oak is a 2002 Minervois while Sweet Chestnut is a 2002 Limoux chardonnay. For further details on how to purchase these wines, visit: www.woodland-trust.org.uk.

Horticultural grants

Information about grants available to those working within horticulture can now be accessed on a new website.

It offers advice on who organises the different grants and the activity for which they are available.
For details visit www.grantsforhorticulturists.org.uk

back to The Garden contents page