Influence of temperature and soil type on the histopathology of Meloidogyne incognita on snap beans

Abstract

Three groups of seedlings of snap bean cultivars Contender and Conquest were planted in Coto clay, Fraternidad silty clay, and San Antón silt loam; inoculated with 10,000 eggs and second stage juveniles of Meloidogyne incognita and placed in growth chambers at 15, 20 and 25° C for 45 days. Multinucleate giant cells with thick cell walls and dense cytoplasm surrounded by proliferation of small cells, breakdown of cell walls, and malformation of vascular bundles were observed. No giant cells were observed in bacterial nodules, even though several of them were invaded by nematodes. Cytoplasmic content of the giant cells decreased as temperature increased. Nematode numbers within roots increased as the temperature increased. There was a tendency for the formation of oval or rectangular giant cells around the vascular bundles and round giant cells in the cortex. Giant cells with the largest number of nuclei were observed at 20° C, and fewer at 25° C. Giant cell was largest at 20 and 25° C, especially in cv Contender. Necrosis or mechanic injury due to migration of juveniles was not observed. The nematodes appeared to develop best in Fraternidad soil.