| heal.abstract |
Forty-six potato gametoclones were obtained from three anther donor genotypes (H2258, AH 78/8015.37a and F115). The response of the anther-derived clones to infection of four root-knot nematode species (Meloidogyne incognita, M. javanica, M. arenaria and M. hapla) was evaluated in a glasshouse experiment. Nematode reproduction rates on different gametoclones was estimated by evaluating egg-masses and galling index for each nematode species. In resistant gametoclones, examined microscopically 21 and 60 days after inoculation, infection sites were absent, or when present exhibited necrotic tissues and giant cells, but were undersized resulting in suppression of nematode development. In the roots of susceptible gametoclones, the nematode completed its development and the egg-laying females fed on well developed giant 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 of alleles involved. Variation for resistance among the gametoclones may be explained by the induction of de novo variability during the regeneration process. |
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