PATHOGENICITY OF MELOIDOGYNE ARENARIA AGAINST TWO VARIETIES OF CARROT (DAUCUS CAROTA L.) IN MEXICO

The relationship between initial inoculation density (Pi) of root-knot nematode, Meloidogyne arenaria, and growth of two varieties of carrot, Magnum and Mexicana, was evaluated in the glasshouse. Initial inoculation densities were 0, 0.25, 0.5, 1, 2, 4, 8, 16 and 32 eggs/g soil. By introducing the values of fresh weight foliage (FWF) and root fresh weight in the model y = m + (1 - m) z (Pi-T), the limit of tolerance (T) was determined as 0.4 and 0.95 eggs/g soil for FWF in Magnum and Mexicana, respectively. The relative minimum yield (m) was 0 in Magnum and 0.3 in Mexicana at a Pi equal to or greater than 32 eggs/g soil. The FWR tolerance limit (T) was 0.25 and 0.75 eggs/g of soil and the relative minimum yield (m) was 0 and 0.1 for Magnum and Mexicana, respectively. Magnum was more susceptible to attack by M. arenaria.