Abstract
Pythium sulcatum was a predominant species isolated from carrot lesions showing brown-blotted root rot, and induced the similar symptoms to those naturally occurring in carrot fields with artificial inoculation. The fungus was also isolated from asymptomatic storage and absorbing roots from seedling to harvest stage, especially during spring cropping season. The infection sites of P. sulcatum was the upper part of asymptomatic storage roots in which the blotted lesion might appear. P. ultimum, P. sylvaticum, P. coloratum and P. spinosum were also obtained from asymptomatic roots and residues of root or leaf, but these species showed slight pathogenicity. The absorbing root residue was found to be the primary infection source of P. sulcatum. P. sulcatum was widespread in the intensive carrot-cultivated area.
