Sorghum Diseases in India

and high humidity. The bacteria are presumed to
gain entry into the plant through wounds, stomata,
or hydathodes. Gaudet and Kokko (1986) detected
P. syringae on 8 to 67% of the sorghum
seeds from different lots, and reported P. syringae
to be the cause of poor sorghum seedling emergence
in Alberta, Canada. They found large numbers
of bacteria inside the seed coat, distal to the
coleorhiza and on the exterior of the seed in the
region of the embryo, after 3 days of germination.
After 7 days, bacteria were observed throughout
the seed, including embryo and endosperm.
Symptoms
Bacterial leaf spot may be difficult to diagnose.
Symptoms resemble pesticide injuries, those of
several fungal diseases, and particularly of older
lesions.
Control recommendations include crop rotation,
destruction of debris, and selecting seed
from disease-free plants. Bacterial leaf spot has
not been reported to be of wide occurrence;
therefore, control measures are not likely to be
warranted.
A recently reported semiselective medium
(KBC) for P. syringae (Mohan and Schaad 1987)
consists of King's B medium supplemented
with boric acid (1.5 mg mL -1 ), Cephalexin® (80
µg mL -1 ), and Cycloheximide ® (200 µg mL -1 ).
This semiselective medium should be advantageous
for isolating P. syringae from plant tissues,
seed, soil, and water, and thus invaluable
in epidemiological and etiological research
(Figs. 5,6,7).
Figure 5. Bacterial spot on sorghum cv B 35-6 caused by Pseudomonas syringae pv syringae.
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