Resistance of fifty-two sweet potato (Ipomoea batatas (L.) Lam) cultivars to the root-knot nematodes, Meloidogyne incognita and M. javanica [Philippines]
1984
Gapasin, R.M.
Rating index, were W-86, L4-89, BPA-4 and Sinibastian; Gold Rush, Binicol, C1596-9, Catanduanes and BNAS 51 were the most susceptible. UPR was the only cultivar found susceptible to M. javanica. Pre- and post-infectional phenomena as mechanisms of resistance occur in sweet potato cultivars. Fewer nematodes penetrated the resistant cultivars Jasper, Jewel and W-86 compared to the susceptible cultivars Binicol and UPR. Histopathology of galled roots in susceptible cultivars showed the formation of multinucleated, thick walled giant cells, hypertrophy and hyperplasia, granulated cytoplasm and displacement or abnormal growth of vascular elements. The resistant cultivars manifested smaller and fewer giant cells, hypersensitivity, and the formation of periderm. Qualitative determination by thin layer chromatography (TLC) showed two distinct blue fluorescent spots in susceptible and resistant sweet potato extracts. Tentative identification of these spots agrees with the Rf values of chlorogenic acid, escopoletin and esculin. More phenolics were accumulated in root extracts of resistant sweet potato cultivars following infection as indicated by the intensity of the color of the fluorescent spots
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