RELATIONSHIP BETWEEN INITIAL POPULATION DENSITIES OF MELOIDOGYNE JAVANICA AND YIELD OF SUNFLOWER IN MICROPLOTS

The relationship between initial population densities (Pi) of Meloidogyne javanica and yield of sunflower was investigated in the field. Microplots were artificially infested with finely chopped nematode-infected tomato roots to give a range of initial population densities (Pi) of 0, o.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256 or 512 eggs and juveniles of M. javanica/cm³ soil. Tolerance limits (T) of 0.74, 0.45, 0.74 and 1.2 eggs and juveniles/cm³ soil were calculated for height, dry top weight, seed yield and see oil content, respectively. Minimum relative yields (m) of 0, 0, 0, and 0.7 were also calculated for height, dry top weight, seed yield and seed oil content, respectively. Maximum nematode reproduction rate (Pf/Pi) was 110.2 at lowest Pi and decreased with increasing nematode population density.