Response of potato gametoclones to infection of four root-knot nematode (Meloidogyne) species

Forty-six potato gametoclones were obtained from three anther donor genotyp es (H(2)258, AH 78/8015.37a and F(l)15). The response of the anther-derived clones to infection of four root-knot nematode species (Meloidogyne incogn ita, M. javanica, M. arenaria and M. hapla) was evaluated in a glasshouse e xperiment. Nematode reproduction rates on different gametoclones was estima ted by evaluating egg-masses and galling index for each nematode species. I n resistant gametoclones, examined microscopically 21 and 60 days after ino culation, infection sites were absent, or when present exhibited necrotic t issues and giant cells, but were undersized resulting in suppression of nem atode development. In the roots of susceptible gametoclones, the nematode c ompleted its development and the egg-laying females fed on well developed g iant cells that had numerous hypertrophied nuclei and granulated cytoplasm. Thirteen anther-derived lines (28%) were resistant to at least one species of root-knot nematode. The resistance to root-knot nematodes was retained through the anther culture process, even when the ploidy level was reduced, indicating that the resistance mechanism is not influenced by the number o f alleles involved. Variation for resistance among the gametoclones may be explained by the induction of de novo variability during the regeneration p rocess.