CURRENT SITUATION AND FUTURE TRENDS IN SOLVING SHARKA PROBLEM IN FR YUGOSLAVIA

Sharka virus is considered to be one of the major factors causing low yields, as intensive plum growing is carried out in the small area still relatively unaffected by sharka, with only 16.3% of the total number of plum trees. In this area, 1.8% of trees were found to be infected in the last screening of infected plum trees. High percentage of infection (50–100%) was found out in all other areas and, as the cultivars grown were of low quality or high susceptibility to sharka, plum growing is at a low agrotechnical level.

In order to find out more permanent solutions to the lasting problems that have arisen due to rapid spread of sharka virus, the work is carried out into several directions:

• In order to control sharka virus in the major growing region, health contol of nursery plum trees is intensified, and permanent control in newly developed and old orchards is conducted. New sources of infection are being destroyed wherever possible.
• Tolerant cultivars, such as Stanley, Cacanska Lepotica and Valjevka are planted in highly sharka-affected regions in order to improve plum growing in these regions. Partially resistant cultivars, such as Cacanska Najbolja, Opal and the plum hybrid WJ-27 are being introduced into production.
• Research on developing immune cultivars of good quality and their introduction into production is intensified. Therefore, the study is being conducted on genetic stability and pomological properties of the following selected, our newly bred hybrids immune to sharka virus: G/8, G/12, G/18, G/19, H/3, 3/15 and 2/83.

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