Sorghum Diseases in India

Colletotrichum graminicola, the causal pathogen
of anthracnose, will cause a panicle and
grain blight under cloudy, warm, and humid
growing conditions. Infected seeds are discolored,
germination is reduced, and seedling
blights may occur. Fungicide seed treatment can
reduce seedling blight. This disease also causes
a stalk and leaf blight, but these are of lesser
economic importance than the grain-blight
phase (Kramer 1958).
Sorghum in storage, like any crop, is subject*
to invasion by Aspergillus and Penicillium spp.
Lopez and Christensen (1963) reported extensive
deterioration occurring at 15-46% moisture.
Pathogens not Seed Transmitted
Seed producers are concerned about yield as
well as seed-quality factors. Therefore, they
must contend with pathogens that do not affect
seeds directly. Maize dwarf mosaic virus
(MDMV) is one example. This virus disease has
reached epidemic status in USA, Europe, South
America, and Australia. Losses in susceptible
cultivars infected during early stages of growth
can approach 100%. Control measures include
destruction of johnsongrass and other susceptible
annual grasses that supply early-season inoculum.
Use of tolerant or resistant cultivars is
another approach. In addition to causing yield
loss, MDMV has been associated with smallseed
production when infection is followed by
periods of low temperature during grain filling
(Edmunds and Niblett 1973).
Rust, caused by Puccinia purpurea, can cause
serious losses in cool, humid areas of Latin
America/southeast Asia, and southern India.
Control is best achieved by resistant cultivars.
Other significant diseases of sorghum that
are not seedborne include gray leaf spot (Cercospora
sorghi), tar spot (Phyllachora sacchari), yellow
sorghum stunt, incited by a mycoplasma,
and crazy top (Sclerospara macrospora).
Stand establishment can be a major problem
in sorghum production, particularly if sown in
cold wet soils (Tarr 1962). The problem is often
caused by seedborne fungi, although soilborne
Pythium spp also causes this. Fungicides have
been effective against common seedborne fungi,
but not against Pythium spp.
300
Conclusion
More than 40 microorganisms are listed as seedborne
on sorghum. This review categorizes
them according to the criteria, of transmission to
the new crop and/or effects on seed growth. The
main inoculum source is seed-transmitted in
only three sorghum diseases. Several other important
diseases are seed-transmitted, but with
these pathogens, residues are usually the more
important inoculum source. Grain molds occurring
in seed-production fields cause serious
losses in seed viability. Fusarium and Curvularia
spp are the major causal agents. There are many
seedborne microorganisms identified in sorghum
that have not been shown to cause a disease
as a result of their presence on seeds.
Nonseedborne pathogens are also a concern in
seed production, because of adverse effects on
seed yields or on seed quality. Soilborne microorganisms
can cause major problems in stand
establishment.
References
Bain, D.C. 1950. Fungi recovered from seed of
Sorghum vulgare Pers. Phytopathology 40: 521-
522.
Bain, D.G, and Alford, W.W. 1969. Evidence
that downy mildew (Sclerospora sorghi) of sorghum
is seedborne. Plant Disease Reporter
53:802-803.
Baker, K.E 1972. Seed Pathology. Pages 317-415
in Seed Biology, Vol. II. (Kowslowski, T.T., ed.)
New York, NY, USA: Academic Press. 447 pp.
Castor, L.L. 1981. Grain mold histopathology,
damage assessment, and resistance screening
within Sorghum bicolor (L) Moench lines. Ph.D.
thesis, Texas A&M University, College Station,
TX,USA.
Castor, L.L., and Frederiksen, R.A. 1980. Fusarium
blight occurrence and effects on sorghum
yield and grain characteristics in Texas.
Plant Disease 64:1017-1019.
Chumaevskaya, M.A. 1962. Charcoal rot of sorghum
and maize. Zasch. Rast. Moskva 7:56.