Histopathology of Beta vulgaris to individual and concomitant infections by Meloidogyne hapla and Heterodera schachtii.

Histological changes in roots of Beta vulgaris cultivar 'USH9A' resulting from infection of Meloidogyne hapla alone, Heterodera schachtii alone, or infection by both species on one feeding site were studied. Anatomical changes caused by M. hapla infection were characterized by regions of hypertrophy and hyperplasia. Giant cells were formed within the stele and varied in numbers from 4-7/feeding site; hyperplasia occurred in the form of a large number of relatively small compacted cells generally surrounding the hypertrophied region. H. schachtii-induced syncytia became dense and muhinucleate. Syncytia were formed in the stele and were limited on the side toward the nematode by endodermis or in part by cortical tissue. Histological changes due to the presence of both parasites on one feeding site were characterized by formation of two distinctive pathological tissues typical of both nematodes. In most infections, xylem elements separated the two pathological tissues. In some sections, a single wall separated the two pathological tissues, and no dissolution of separating wall was noted in any sections. Each nematode developed normally and produced its own characteristic pathological tissue independently.