Studies on the Histopathological Responses of Vigna Mungo towards Meloidogyne Incognita at Different Time Intervals

Abstract

The pot experiments on Vigna mungo with five replicates for each treatment were set up in the Department of Botany, Aligarh Muslim University, Aligarh, Uttar Pradesh (27°52’59” N to 78°04’59” E; 180 m above sea level), India. Histological studies of the roots of infected plants were carried out after 24 h, 48 h, 72 h, 5 days, 10 days, 15 days, 21 days, 25 days and 30 days of inoculation. The second-stage juveniles penetrated into the roots and moved intercellularly by separating the cell walls after 24 h. The first sign of infection observed after 48 h of inoculation was hypertrophy in the cells, around the head of the juvenile. The cytological changes in the hypertrophied cells became more prominent after 72 h of inoculation, and the cells transformed into discrete giant cells. The giant cell cytoplasm became dense and stained darkly, the size of the nuclei and the nucleoli increased after five days of inoculation. Ten days after inoculation, the width of vessel elements was also increased. The second-stage juveniles moulted into the third stage. After 21 days of nematode exposure, the hypertrophied and hyperplastied parenchyma cells were observed adjacent to the giant cells. At several occasions, the giant cell complexes appeared to be surrounded by abnormal xylem comprising of abnormal vessel elements, which were transformed from the hypertrophic and hyperplastic parenchymatous tissue. The head region of the nematode was in contact with the giant cells while remaining part of the body expanded and caused disruptions in the arrangement of vascular and cortical tissues, as was observed after 25 days of inoculation. After 30 days of nematode inoculation, egg masses were found associated with all the mature females. The tissues were disrupted as the egg masses were pushed out to the surface of the root. Several eggs enclosed first stage juveniles.