Articles
The problem of sharka – control and prevention measures in the last four decades
Article number
1260_16
Pages
91 – 104
Language
English
Abstract
During the first four symposia of our working group, the dangerous virus disease sharka was paid little attention, despite the fact that the disease (caused by Plum pox virus; PPV) was already widespread in Europe.
In the 1970s, PPV was an important research subject for virologists.
In fruit growing, the real problem of sharka was not recognized, and the disease could spread rapidly.
In the 1980s, the problem of sharka in fruit growing was appreciated for the first time.
By adopting programmes for eradication of infected trees and planting virus-free plant material, it was hoped to stop the devastating virus disease.
At the same time, the search for tolerant and resistant cultivars began.
The above-mentioned measures could not inhibit the spread of PPV. As in nearly all Central European countries, plum trees and also wild plums are widespread in the landscape in Germany; eradication control is not realistic and is, therefore, no longer conducted.
In the 1990s, methods for screening of PPV-resistant cultivars were developed in different countries, and new breeding programmes were started.
Time and money were spent to develop more sensitive detection techniques, and virus-free mother trees of many cultivars were established.
There were reports of immune wild types and cultivars.
However, at the symposium in Warsaw in 1997, the board came to the resolution that, at that moment, no immune genotypes were known, and the chance of them being found was very low.
With the discovery of the hypersensitive reaction of plums to PPV in 1986, a new possibility in resistance breeding was found, resulting in the first absolutely PPV-resistant cultivar Jojo in 1999. As a consequence of the quantitative resistance, which depends on climatic conditions, more and more fruit growers became dissatisfied with the resistance or tolerance to PPV of currently cultivated plum cultivars.
A new approach to the development of resistant cultivars was genetic transformation.
In the 1990s, many research programmes based on gene transfer were started in different countries.
The transformation of Prunus domestica using Agrobacterium tumefaciens made it possible to engineer the PPV coat protein (CP) gene in plums.
The C-5 clone was selected and later introduced as cultivar Honeysweet. However, we should also take in consideration that, in most European countries, the cultivation of genetically modified plants is not allowed, and consumers do not want food derived from such plants.
An alternative to obtain completely resistant cultivars is to combine cultivars and rootstocks with hypersensitivity resistance to PPV. In the meantime, four hypersensitive cultivars are on the market, and also two hypersensitive rootstocks.
In the 1970s, PPV was an important research subject for virologists.
In fruit growing, the real problem of sharka was not recognized, and the disease could spread rapidly.
In the 1980s, the problem of sharka in fruit growing was appreciated for the first time.
By adopting programmes for eradication of infected trees and planting virus-free plant material, it was hoped to stop the devastating virus disease.
At the same time, the search for tolerant and resistant cultivars began.
The above-mentioned measures could not inhibit the spread of PPV. As in nearly all Central European countries, plum trees and also wild plums are widespread in the landscape in Germany; eradication control is not realistic and is, therefore, no longer conducted.
In the 1990s, methods for screening of PPV-resistant cultivars were developed in different countries, and new breeding programmes were started.
Time and money were spent to develop more sensitive detection techniques, and virus-free mother trees of many cultivars were established.
There were reports of immune wild types and cultivars.
However, at the symposium in Warsaw in 1997, the board came to the resolution that, at that moment, no immune genotypes were known, and the chance of them being found was very low.
With the discovery of the hypersensitive reaction of plums to PPV in 1986, a new possibility in resistance breeding was found, resulting in the first absolutely PPV-resistant cultivar Jojo in 1999. As a consequence of the quantitative resistance, which depends on climatic conditions, more and more fruit growers became dissatisfied with the resistance or tolerance to PPV of currently cultivated plum cultivars.
A new approach to the development of resistant cultivars was genetic transformation.
In the 1990s, many research programmes based on gene transfer were started in different countries.
The transformation of Prunus domestica using Agrobacterium tumefaciens made it possible to engineer the PPV coat protein (CP) gene in plums.
The C-5 clone was selected and later introduced as cultivar Honeysweet. However, we should also take in consideration that, in most European countries, the cultivation of genetically modified plants is not allowed, and consumers do not want food derived from such plants.
An alternative to obtain completely resistant cultivars is to combine cultivars and rootstocks with hypersensitivity resistance to PPV. In the meantime, four hypersensitive cultivars are on the market, and also two hypersensitive rootstocks.
Authors
W. Hartmann, M. Neumüller
Keywords
Prunus domestica, Plum pox virus, sharka resistance, hypersensitivity, plum cultivars, genetically modified plums
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