THE EFFECT OF POPULATION DENSITIES OF MEOIDOGYNE INCOGNITA ON YIELD OF SUSCEPTIBLE AND RESISTANT TOMATO

The relationship between initial population densities of Meloidogyne incognita race 1 and yield of susceptible and resistant tomato cultivars was investigated in the field. Microplots were infested with finely chopped nematode infected pepper roots to give a range of population densities of 0, 0.031, 0.062, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64 or 128 eggs and juveniles/cm³ soil. A tolerance limit (T) of 0.55 eggs and juveniles of M. incognita/cm³ soil was calculated for both cultivars of tomato. A minimum relative yield (m) of 0 and 0.7 at initial population densities (Pi) = 32 eggs and juveniles/cm³ soil was also calculated for the susceptible and resistant tomato cultivar, respectively. Fruit size and marketable yield of tomato of the susceptible cultivar were negatively affected by the nematode infestation. Maximum nematode reproduction rate was 1,539 at the lowest Pi on the susceptible tomato but decreased with increasing nematode population density. Reproduction rate was lower that 1 at all initial population densities of M. incognita in microplots planted with the resistant tomato cultivar.