Sorghum Diseases in India

upwards of 20 cm with the leaf and leaf sheath
nearly encompassed with symptoms. Bacterial
stripe symptoms are often similar to those of
bacterial streak, and both closely mimic those of
several fungal diseases.
Although research data on field dissemination
are not available, it is probably by wind and
rain. Infested seed or debris probably account
for long-distance dissemination. Weed hosts,
volunteer plants, and infested seed are likely
sources of overseasoning bacterial organisms.
Sources of tolerant and susceptible germplasm
are listed in Table 2.
Table 2. Reaction of selected sorghum lines to
bacterial stripe (Pseudomonas andropogonis)
and bacterial streak (Xanthomonas campestris
pv holcicola).
Rating 1
Line Stripe Streak
80 B 3039-5 6.0 5.8
Tx 2783 5.8 2.2
B 35-6 5.6 2.6
81 BH 5359 5.6 5.1
81 BH 5426 5.6 3.3
Tx 2536 5.6 4.2
77 CS1 5.6 4.1
76 CS 478 5.0 5.6
76 CS 256 (TS) 4.8 5.5
GR 2-14-1 3.7 5.4
81 L- 13688 4.6 5.4
81 BH 5496 2.5 2.3
R 6956 2.5 2.5
R 3338 2.5 1.0
SC 326-6 2.5 2.2
81 BH 5559 2.4 2.5
BTX 378 1.7 2.2
QL 3 (India) 1.5 2.1
81 BH 5646 2.0 2.2
CV 223-4-1-1 3.1 2.2
SC 170-6-17 5.0 2.0
9 L-3510 3.0 1.5
1. Ratings based on the percentage of leaf area with
symptoms defined as follows: 1 = trace 56%, and 6 = all
plants dead.
Source: Clafin and Rosenow (1983)
138
Temperature and relative humidity
A susceptible genotype of P. andropogonis
(80 B 3039-5) from the Texas A&M University
All Disease and Insect Nursery (ADIN) was
used to determine the optimal temperature and
relative humidity for bacterial stripe development
in sorghum (Claflin and Machtmes,
unpublished). Plants were inoculated with a
Hagborg device (Hagborg 1970) at the four-leaf
stage of growth and then placed in growth
chambers at relative humidity levels of 90, 75,
and 50%. Temperature combinations were 24/18
(16 h day/8 h night), 30/24, and 36/24°C. Plants
were rated, 2 weeks after inoculation, on the
percentage of leaf area with symptoms. Ratings
were defined as follows: 1 = trace -1%; 2 = 2 -
10%; 3 =11 -25%; 4 = 26 -50%; 5 - 50%; and 6 =
death of plant.
Significant differences in disease expression
of P. andropogonis were observed between the
three RH levels, with maximum ratings at the
90% level. Disease expression was maximum
(overall rating of 3.3) at 30/24°C. Significant differences
were also observed at temperatures of
36/24°C and 24/18°C (ratings of 2.5 and 2.2,
respectively).
Bacterial Leaf Blight
Causal organism
P. avenae (Syn. P. alboprecipitans) is the causal
agent of bacterial leaf blight disease of maize,
oats, barley, wheat, Italian millet, barnyard millet,
proso millet, foxtail millet, finger millet, rice,
and rye (Rosen 1922; Schaad et al. 1975; Shakya
et al. 1985; Bradbury 1973a). P. avenae cells are
aerobic, gram-negative, with dimensions averaging
around 0.6 x 1.8 µm. Acid is produced
from arabinose, fructose, galactose, glucose,
glycerol, and sorbitol. Citrate and malonate are
utilized as sole sources of carbon. Starch and
gelatin are not hydrolyzed. Growth occurs at
41 °C, but not at 4°C. Lipase and oxidase are produced
and nitrates are reduced. Colonies growing
on YDCA are smooth, round, and viscid,
and are cream-colored with a brownish tinge. A
halo may be detected around colonies when the
pH of the medium is 6.8 or less and contains
beef extract (Claflin and Ramundo, unpublished).