THE GENOME SIZE AND CHROMOSOME COMPLEMENT OF THE POTATO CYST-NEMATODEGLOBODERA-PALLIDA

The genome size of Globodera pallida was estimated by direct microdens itometry of stained somatic nuclei in comparison to those of Caenorhab ditis elegans. There was no significant difference between the genome sizes of these nematodes and thus the genome of G. pallida is estimate d to be composed of 1 x 10(8) base pairs. This value is of the same or der as genome sizes calculated previously for a variety of other nemat ode species. Chromosomes in the dissected gonads of G. pallida females were visualized using five staining methods: propionic acid/orcein, F eulgen, Giemsa and two fluorescent stains, DAPI (4'6-diamidino-2-pheny lindole) and Hoechst 33258 (Bisbenzimide). Propionic acid/orcein prove d to be the best staining method and despite the small size of the chr omosomes it was used to demonstrate that G. pallida has a diploid chro mosome complement of 18 (n = 9).