Epsilon Open Archive

Abstract

The potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, major parasites of potatoes, were found for the first time in Sweden in 1922 and 1965, respectively. The objective of the thesis was to expand the knowledge of Swedish PCN populations by studying morphological/morphometric diversity, population genetics, virulence and biology in order to improve the control basis. The most commonly used differential morphological/morphometric characters of the two PCN were examined to estimate the degree of inter- and intraspecific variation. PCR analysis was performed on each specimen to ascertain the species to which it belonged. An absolute separation of the species could not be achieved on the basis of individual characters, but the probability of making the right identification was substantially improved by combining two or more characters. This suggested that the development of a computer expert system might be profitable. The same characters as for PCN, expanded with some egg and larval dimensions, ware used to characterise a non-PCN Globodera population that might be confused with PCN. Data corresponded well with the morphometry of three foreign populations of G. artemisiae. Identification was fortified by sequence analysis of ribosomal DNA internal transcribed spacers (ITS), whereby the first record of G. artemisiae in Sweden could be established. The extent of genetic polymorphism and relationship between Swedish and foreign PCN populations was estimated in an AFLP study. There was a large heterogeneity in both species. Swedish G. pallida populations seemed to originate both in the British Isles and in continental Europe. A combined method and virulence test of Swedish and foreign PCN populations proved the occurence of virulence groups Ro 1,4, Ro2,3 and Pa2,3 in Sweden. The "closed container" test method appeared accurate enough for advisory samples. A simplified protocol, which combines the advantages of traditional bio-tests and PCR techniques, is suggested. Hatching experiments verified that G. pallida is better adapted to a colder climate than G. rostochiensis. Populations of the latter species from early potato districts and from a northern region hatched at lower temperatures than populations from the main crop potato districts in southern Sweden, suggesting the commencement of an adaptation process.