Sorghum Diseases in India

The Striga spp are invariably a major problem
in almost all countries in eastern Africa, and
heavy crop losses from severe infestation by
these parasitic weeds are common. In Uganda,
losses due to Striga can be as much as 30% (Esele
1986); in western Tanzania, the parasite caused
up to 40% loss in yield (Shao 1985). In Sudan and
Ethiopia, the widespread Striga spp have forced
farmers to abandon their land (Elizen 1986).
At country levels within the region, the following
five diseases are ranked in the order listed
(Guiragossian 1986).
Burundi; Ergot, anthracnose, rust,
charcoal rot, and Striga.
Ethiopia: Striga, anthracnose, grain mold,
covered smut, and ergot.
Kenya: Striga, grain mold, leaf blight,
covered kernel smut, and head
smut.
Rwanda: Leaf blight, ergot, covered smut,
downy mildew, and Striga.
Somalia: Covered smut, loose smut, head
smut, charcoal rot, and
anthracnose.
Sudan: Striga, charcoal rot, long smut,
leaf blight, and anthracnose.
Uganda: Grain molds, smuts,
anthracnose, leaf blight, and
Striga.
Research Activity
Research attention to sorghum diseases is much
more evident than it was 10 years ago. Surveys
to identify diseases have been carried out in
most countries, and the major diseases have
been categorized according to importance. Specific
studies of sorghum diseases have received
less emphasis.
Breeders were highly involved in selecting
breeding materials, using disease resistance as
one criterion in selection. Special research projects
set up to develop resistant lines exist in
Ethiopia, Uganda, and Kenya. However, within
the past 10 years, pathologists have been included
in the Sorghum Improvement Program,
and some progress has been made in searching
out and incorporating resistance into the breed
ing lines. Cases in point include screening for
resistance to sorghum anthracnose, grain molds,
and downy mildews. International Disease and
Insect Nursery programs are in operation.
The assistance of ICRISAT in this regard
is invaluable. Much collaborative work is underway.
A backcrossing program has even been initiated
in Ethiopia in an attempt to incorporate
resistance to anthracnose from exotic sources to
indigenous elite lines. Some success has been
achieved in restoring genes for resistance into
selected Ethiopian lines.
Independent studies likewise have been carried
out to evaluate indigenous as well as exotic
lines for resistance to different isolates of Colletotrichum
graminicola and to other leaf diseases.
However, except in a few cases, factors conditioning
resistance have not been worked out,
and in most cases the stability and durability of
the lines is not clearly understood, perhaps due
to the changing virulence of the pathogen. To
reduce the influence of variability in virulence of
the isolates, some workers are testing advanced
lines in a wide range of ecological zones.
This closer attention to pathological problems
reflects the growing importance given to sorghum
in eastern Africa, and efforts to utilize its
tolerance to drought-stress and its adaptability
to wider ecological zones to meet the growing
demand for staple food.
Sorghum Disease Control
Among the many alternative measures listed by
Frederiksen (1985), selecting for disease resistance
has been the most important approach so
far taken. Evaluating on the basis of reaction of
elite lines to the prevailing important diseases
before release for large-scale production is now
a common practice.
Seed-dressing with chemicals against smuts
is practiced in many instances, though it is not
widely accepted by peasant farmers.
In Somalia, where damage by covered and
loose kernel smuts has at times reached the 40%
level (Alahaydoian and Ali Nur Duale 1985),
evaluation of seed-dressing chemicals was
initiated.
Some countries, such as Kenya, have a strong
quarantine procedure to exclude diseases considered
to be dangerous. However, with more
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