The composition of southern root-knot nematode (Meloidogyne incognita) race in the resistance test field used for sweetpotato breeding

It is important to clarify the nematode race composition in a resistance test field where many crop varieties are cultivated, because several nematode races may occur. According to parasitism to sweet potatoes, the southern root-knot nematode (Meloidogyne incognita) population in a field in Katori-city showed a race SP4-like response, although the dominant race had been determined SP6. To clarify the reason, we examined the race composition using 16 nematode lines each derived from a single egg-mass. We concluded that average responses based on the dominant SP6 and the minor SP2 might have shown the response of SP4 as a population.