Differences in the resistance of sweet potato cultivars and lines to Melodogyne incognita populations

Differences in resistance of sweet potato cultivars to some populations of Meloidogyne incognita were examined in greenhouse assays. Twenty-four major sweet potato cultivars rooted in 200 g of potted soil were inoculated with approximately 500 juveniles of four M. incognita populations collected from different areas. Reproduction rates (eggs produced per J2 inoculated) were determined after 35 days of growth at 27°. Nine cultivars with reproduction rates higher than 11 were rated as susceptible and five cultivars with reproduction rates lower than one were rated as highly resistant to the four populations. However distinct differences were observed in reproduction rates of those populations on the other 10 cultivars. In an assay similar to the one described above with 13 newly developed cultivars or breeding lines, all four populations produced many egg-masses on three and produced only a few egg-masses on 6 of those cultivars or breeding lines. However, the remaining cultivars or breeding lines did not have a consistent response to the four populations. Among purple sweet potato cultivars grown primarily in Okinawa and Tanegashima Island, two similarly shaped cultivars, Bise and Tanegashima-murasaki 7, exhibited different levels of resistance to two populations as indicated by a marked difference between the numbers of egg masses produced. These results clearly demonstrate that resistance of sweet potato to populations of M. incognita distinctly differs with cultivars or breeding lines. Jpn. J. Nematol. 32 (2), 77-86 (2002).