There are four known physiological races of the southern root-knot nematode [Meloidogyneincognita (Kofoid & White) Chitwood]. Races are designated I through 4 and their identifications are based soley on differential hosts. These race problems as related to breeding sweetpotato for resistance to attack by all races are reviewed and discussed. Data are presented showing the reactions of selected cultivar and breeding clones of sweetpotato to all four races. The reactions of races 1 and 3 are generally well—known. Races 2 and 4 apparently are spreading and becoming more numerous in the southern states where soybean and tobacco are grown. Comparative disease indices are presented showing that generally sweetpotatoes were less susceptible to races 2 and 4. However, there were some notable exceptions, for example, `Sulfur' and `Beauregard' were equally susceptible to all races. High resistances to attack by races 2 and 4 were found in `Sumor', `Nemagold', `Excel', W-241 and others.
If the inline PDF is not rendering correctly, you can download the PDF file here.