Differences in parasitism of Meloidogyne incognita and two genotypes of M-arenaria on Solanum torvum in Japan

Two genotypes of root-knot nematode, Meloidogyne arenaria (A2-O and A2-J), are found in Japan. They were distinguished from each other based on mitochondrial DNA sequences. The primer set (C2F3/1108) amplified a 1.7-kb fragment from A2-J, whereas a 1.1-kb fragment was amplified from A2-O. M. arenaria (A2-O) was detected in local regions of southern Japan, whereas M. arenaria (A2-J) was widespread from the Kyushu region to the Tohoku region. The distribution of M. arenaria (A2-J) overlaps with the cultivation area of eggplant. Solanum torvum is used worldwide as a rootstock for eggplant cultivation, and it is resistant to Meloidogyne spp. In particular, it is reported that S. torvum is resistant to M. arenaria outside Japan. In this study, we inoculated S. torvum rootstock cultivars with M. arenaria (A2-J), M. arenaria (A2-O) and Meloidogyne incognita populations. Although M. incognita and M. arenaria (A2-O) produced only a few egg masses on S. torvum, thereby confirming its resistance, the four geographical populations of M. arenaria (A2-J) produced large numbers of egg masses on S. torvum. This study confirmed that S. torvum is resistant to M. incognita and M. arenaria (A2-O) populations, but susceptible to populations of M. arenaria (A2-J) in the eggplant production area of Japan.