Sorghum Diseases in India

All P. rubrilineans strains tested were pathogenic
to maize, sorghum, and millet and, except
for strain NCPPB 3112, to sugarcane. Lesions on
those plants were indistinguishable from those
of P. avenae. With some strains, a hypersensitivelike
reaction was observed on maize, sorghum,
and millet. Within 24 to 48 h after inoculation
with the Hagborg device, the tissue subjected to
inoculation became necrotic, assuming a translucent
appearance. Within 3 or 4 days, the translucent-like
areas turned light brown but failed to
enlarge, remaining confined to the tissue infiltrated
by the Hagborg. Inoculations with PBS
showed only the injury caused by the Hagborg,
without necrosis.
Most strains of P. rubrisubalbicans were pathogenic
to sugarcane, although several provided
weak reactions. With the exception of strain PD-
DCC 3109, the other strains were negative or
caused hypersensitive reactions on maize, sorghum,
and millet. The hypersensitive reactions
appeared to be identical to those for P. rubrilineans,
described above. Strain PDDCC 3109 on
maize produced circular to rectangular watersoaked
areas around the light brown and/or
translucent necrotic areas. Water-soaking consisted
of small areas resembling freckles, usually
with a yellow halo around the periphery.
Sorghum lesions were small (1-3 mm) circular
to rectangular dark brown areas, with light
brown zones or streaks radiating from the primary
lesion. Lesions were also characterized by
light yellow areas around the periphery. On millet,
tan water-soaked areas were most noticeable
as-narrow streaks and were not necessarily vein
delimited. On older lesions, light brown necrotic
areas surrounded by tannish water-soaked areas
were characteristic.
The pearl millet isolate incited symptoms on
maize, sorghum, millet, and sugarcane and
symptoms were identical to those incited by
P. rubrilineans and P. avenae.
Strains of P. andropogonis were most virulent
on maize and sorghum, mildly virulent on sugarcane,
and provoked a weak response on
millet.
Antisera production of P. andropogonis
and P. avenae
Pseudomonas avenae (syn P. alboprecipitans)
strains ATCC 19860 and ICPB PA134, P. an­
dropogonis strains ATCC 23061 and ATCC 23062,
P. rubrilineans strain ATCC 19307, P. rubrisubalbi
cans strain ATCC 19308, and P. syringae pv syringae
strains ICPB PS 146 and PS 296 were utilized
as antigens in antisera production, The
bacteria were grown on YDCA for 96 h at 28 °C
and washed with sterile 10 mM PO4 buffered
saline (0.85% NaCl, pH 7.2) [PBS] by centrifuging
three times at 17 000 g. Cells were resuspended
in PBS and fixed by dialyzing against a
2% glutaraldehyde solution at room temperature
for 3 h. The cells were then dialyzed for 24-
36 h against 100-fold volumes of PBS (with five
or six changes). Equal volumes of bacterial suspensions
(ca. 2 x 10 10 cfu mL -1 ) and Freund's
incomplete adjuvant (Difco) were emulsified
with the aid of a Spex mixer-mill for 2 min at
high speed.
New Zealand white rabbits were injected intramuscularly
with one mL of the emulsfied suspension
at weekly intervals. Rabbits were bled
from the marginal ear vein after the fourth injection.
Injections continued until serial two-fold
agglutination titers exceeded 1:2048. Sera were
collected 3 to 4 h after bleeding and stored in
serum bottles without preservatives at -20 °C
Dot-immunobinding assay, P. avenae and
P. andropogonis
The dot-immunobinding assay (DIA) was performed
(DeBlas and Cerwinski 1983; Leach et al.
1987) using Schleicher and Schuell (Keene, NH)
nitrocellulose membranes (0.2 mm, BA83) which
were divided into 1 x 1 cm squares by marking
with a ballpoint pen, washed in distilled water
for 5 min and air dried before use. Four mL of
serial 10-fold dilutions of the bacterial cultures
were individually spotted on the grids. Distilled
water was used as a control. Each nitrocellulose
membrane was cut into strips (4- x 6-cm) in
which the serial dilutions (normally four) were
arranged in a top to bottom descending order of
dilution. The bacterial cells were fixed to membranes
by soaking in 10% acetic acid and 25%
ethanol solution for 15 min. This was followed
by a rinse in distilled water and then another
rinsing in three or four changes of 50 mM Tris-
HC1 (pH 7.2) containing 200 mM NaCl and 0.1%
Triton X-100 (TBS-T100). Antiserum was diluted
in TBS-T100 to 1:2000 (v/v). The membranes
were incubated in the antiserum dilution for 2 h
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