Black rot (Xanthomonas campestris p

Black rot (Xanthomonas campestris pv.
campestris, X. campestris pv. maculicola, X.
campestris pv. raphani) – Seedborne
Radish is susceptible to all three pathovars of X.
campestris that can infect crucifers. This can be a
very serious disease of crucifers, including radish.
Symptoms vary greatly depending on the age of
the plant when infected, as well as the pathovar
and the particular strain of the pathovar.
campestris pv. raphani and X. campestris pv.
maculicola attack the leaves and petioles, causing
small tan to white spots with narrow, yellowish,
water soaked zones on the leaves. The spots on
the leaf petioles are black, sunken, and elongated.
Severe infection results in defoliation and, in
extremely severe cases, death may occur. X.
campestris pv. campestris can cause angular, Vshaped
yellow lesions that typically develop along
the leaf margin, because the bacterium readily
enters the leaf where the veins end at the leaf
margin and form an opening called a hydathode.
The veins in these yellow lesions may turn black.
The lesions can dry up and turn brown. Severely
infected leaves drop off the plant. Infection can
turn systemic, i.e., the pathogen moves from the
leaf into the petiole, the branches, and the main
stem. If so, the vascular tissues turn black.
Different races of the pathogen have been
reported. In seed crops, infected plants may be
symptomless, but systemic infection can lead to
movement of the pathogen into the pods and seed.