Sorghum Diseases in India

at room temperature, or overnight at 4°C, and
then rinsed in four changes of TBS-T100 with 5
min for each rinse. The strips were then incubated
for 2 h in protein A-alkaline phosphatase
conjugate (Sigma, St. Louis, MO) diluted (1:1000;
v/v) in TBS-T100. The membranes were rinsed
in TBS-T100 followed by two rinses in Tris-buffered
saline. Following washing, the strips were
placed in a substrate solution [12 mg fast violet B
salt (Sigma), 2 mL Napthol AS-MX phosphate
alkaline solution (Sigma), and 48 mL distilled
water] for 30 min on a tabletop shaker in the
dark. The substrate was prepared immediately
before use. The strips were then rinsed with running
tap water for 5 to 10 min and air-dried.
Positive reactions gave a violet color (Fig, 4).
P. avenae (ATTC 19860) antiserum used in
DIA tests did not distinguish P. rubrilineans,
P. avenae, and the millet strain at dilutions of 10 5
(Fig. 4). Comparable results were obtained with
P. rubrilineans antiserum. Faint cross-reactions
were observed at a dilution of 10 8 for P. syringae
pv syringae and at dilutions of 10 7 and 10 8 for
10 8
10 7
10 6
10 5
P. rubrisubalbicans. In several experiments,
P. rubrilmeans, P. avenae, and the millet strain
provided faint confirmation readings at dilutions
of 10 5 (approximately 800 colony-forming
units per application). Therefore, we concluded
that P. avenae, P. rubrilineans, and the millet
strain are synonymous.
The bacterial pathogen affecting millet production
in northern Nigeria was identified as
P. avenae on the basis of biochemical, physiological,
and immunological tests. The millet pathogen
and P. rubrilineans were synonymous to
P. avenae strains and were clearly distinct from
the closely related pathogen P. rubrisubalbicans
(Claflin and Ramundo, unpublished). Zummo
(1976) described a yellow leaf blotch of maize,
sorghum, and pearl millet in western Africa
with symptoms partially resembling those we
observed on pearl millet. His photographs reveal
a more oval-shaped lesion, closely resembling
symptoms of Striga spp, although it was
described as vein-limited. Bacterial stripe symptoms
that we observed were always vein-limited
A B C D E F G
Figure 4. Nitrocellulose membrane from a dot-immunobinding assay of various bacterial causal
agents including P. syringae pv syringae (A), P. andropogonis (B), P. avenae (C), P. rubrilineans
(D,E), P. rubrisubalbicans (F), and water control (G). P. rubrilineans antiserum was used at a
dilution of 1:1000.
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