Suomessa viljellyn perunan virustautisuudesta

Authors

• Klaus Aura Kasvitautien tutkimuslaitos, Tikkurila

DOI: https://doi.org/10.23986/afsci.71416

Abstract

In 1955 the Department of Plant Pathology set to work, on Professor E. A. Jamalainen’s iniative, to study serologically the occurrence and distribution of potato viruses X and S in Finland and their prevalence in different potato varieties. In 1955 determinations of potato leaf material were made by Mr. A. B, R. BEEMSTER of the Institute for Phytopathological Research at Wageningen, Holland, who worked in the Department of Plant Pathology in August-October 1955. He analysed serologically leaves of potato plants, of which 450 samples had been collected from different potato experiments, the rest. 100 samples, coming ’from farmers’ fields. In the period of growth in 1956, the serological determinations were continued, and in addition a great number of visual observations of potato virus diseases were made on the basis of symptoms. A total of 650 potato plants were analysed; one half the plants coming from different potato experiments and the other half from farmers’ fields, althogether from 79 communes. The serological virus determinations were made in accordance with the agglutination method. The needed antisera and normal sera had been received from Holland (Laboratorium voor Bloembollenonderzoek). Table 1, p. 104 shows the occurrence of virus S and virus X in different parts of the country in 1955—56. It appears that viruses S and X are rather prevalent in the whole of Finland wherever potato is grown. According to the data in Table 1 it is possible to conclude that in Finland virus S would be to some extent more common than virus X. In fact the contrary appears to be true. In the studied material there was a great deal of the Jaakko potato variety, which was heavily infected by virus S. This variety is, indeed, comparatively little cultivated in Finland. Instead, the Eigenheimer variety, which is by far the most commonly cultivated potato in this country (18), is very much infected by virus X (Table 2, p. 105). Fields completely infected by virus X and virus S are very common in Finland. Nearly all the examined potato fields were at least partly infected either by both of these viruses or by one of them. Only 10 % of the studied 105 fields were without virus infection according to serological determinations and visual observations. The losses caused by potato Crincle mosaic are, according to observations, mostly slight or moderate in Finland. They are very common in the southern and southwestern parts of Finland and in the coastal region of South-Ostrobothnia (West Finland). Information concerning the general losses caused by potato Crincle mosaic in Finland is not available. According to the work of BRUMMER (2), the slight type of Crinkle mosaic lowered the yields by 22 % and the more severe type by 64 %. Rugose mosaic caused by a combination of X and Y viruses occurs mostly in isolated cases in South Finland. Streak and Rugose caused by virus Y, which was determined on the basis of the symptoms, has been found in Finland only in isolated cases in the southern parts of the country. The spreading of virus Y Rugose in Finland may be connected with the prevalence of the virus spreading aphids. Fields totally infected by virus Y have not been found. Even in the badly infected potato fields only 5—15 % of the plants proved to be infected with virus Y. Potato Leaf roll seems of minor significance in Finland as has earlier been established by JAMALAINEN (6). This disease was, however, abundant in 1956 on some Local Experimental Stations, though mainly on the Dore and Saskia potato varieties, which, being imported from abroad, were probably already infected. Table 2 p. 105 presents a summary of the serologically determined virus X and virus S on different potato varieties. Those varieties, of which a number of samples had been received from different parts of the country, proved to be, according to the serological determinations, approximately similarly infected by viruses throughout the country. The Jaakko potato variety proved very heavily infected by virus S; virus X, on the other hand, was less to be found. Virus S occurred in the Jaakko variety almost latent; the leaves were only slightly convex between the veins. Virus X was abundant on the Eigenheimer potato variety. Virus S was also relatively abundant in this variety. The same applies to the Rosafolia potato variety, which is the most cultivated variety in Finland after Eigenheimer. Varieties belonging to groups of the miscellaneous and unknown potato varieties were also particularly virus infected; the cultivated area of these is even larger than that of Eigenheimer (18). It was interesting also to establish that the country potato variety Hettula, cultivated only in North Finland, was severely infected by virus S and virus X. In the Hettula variety, as in many other varieties, viruses X and S could be simultaneously latent in the same plant. The newer potato varieties cultivated in Finland, such as Siikli and Akvila, were only slightly infected by viruses. The Akvila variety was, however, at a Carelian Local Experimental Station, very heavily infected by virus X.