Abstract
To use resistant cultivars of sweetpotato effectively occurrence and distribution of pathogenic races of M. incognita were examined. Five sweetpotato differential cultivars, ‘Norin-1’, ‘Norin-2’, ‘Tanegashimamurasaki-7’, ‘Elegant Summer’ and ‘J-red’, which were selected from major Japanese sweetpotato cultivars based on resistance response to four M. incognita populations with different virulence were used as differential hosts. A total of 129 M. incognita populations were collected from mainly sweetpotato fields in Kyushu and Okinawa, Japan. Reproduction of the populations was assessed on the differentials based on production of egg-masses and pathogenic races were designated. Nine races, SP1 to SP9, were identified from these populations and 37.2%, 43.4% and 7.0% of the populations were, respectively, race SP1 that reproduces only on ‘Norin-1’, SP2 that reproduces on both ‘Norin-1’ and ‘Norin-2’, and SP4 that reproduces on four of the differential hosts but not on ‘J-Red’. Region specific distribution was observed in these races. SP1 was widely distributed in Kumamoto and northern prefectures. SP2 was predominant in southern Kyushu, in both Miyazaki and Kagoshima Prefectures. SP4 was the major race in Okinawa Prefecture. Other races were detected from limited areas. Jpn. J. Nematol. 35 (1), 1-12 (2005).
