GENE POOL SIMILARITIES OF POTATO CYST-NEMATODE POPULATIONS ASSESSED BY AFLP ANALYSIS

AFLP was used to characterize 24 potato cyst nematode populations. Thi s novel DNA fingerprinting technique enabled the identification of 987 marker loci by screening only 12 primer combinations. Data on presenc e or absence polymorphisms and data on the intensities of correspondin g DNA fragments were collected. Separate analysis of both data sets re vealed similar dendrograms for the nine G. rostochiensis populations i ncluded in this study. Both dendrograms consisted of two groups contai ning three and five related populations, respectively. One population differed from either of these groups. Each group represented a differe nt pathotype as defined by Kort et al. (J, Kort, H. Boss, H. J. Rumpen horst, and A. R. Stone, Nematologica 23:333-339, 1977). Previously, a similar arrangement was found after analysis of the genetic variation using random amplified polymorphic DNA (RAPD) (R. T. Folkertsma, J. N. A. M. Rouppe van der Voort, M. P. E. van Gent-Pelter, K. E. de Groot, W. J. van den Bos, A. Schots, J. Bakker, and F. J. Gommers, Phytopath ology 84:807-811, 1994). For the 15 G. pallida populations analyzed, c omplex AFLP patterns were obtained and therefore only qualitative AFLP data were used. Incongruities were observed between clustering on the basis of AFLP data and classical pathotyping. This strongly confirms earlier findings obtained with RAPDs, because the AFLP markers used in this study outnumbered the population characteristics revealed by RAP Ds by a factor of five. To arrive at a reliable pathotype designation of potato cyst nematode populations molecular data and virulence chara cteristics should be integrated. Possible causes for the difference in distribution of polymorphisms among G. rostochiensis and G. pallida p opulations are discussed.