Sorghum Diseases in India

Symptoms
C. graminicola infects leaves, stalks, peduncles,
panicle, and the grain, either separately or all
together (Pastor-Corrales and Frederiksen 1980).
These disease symptoms include a foliar phase,
stalk rot, and panicle and grain anthracnose.
These different phases of anthracnose often
manifest as apparently different diseases.
The characteristic symptoms caused by
C. gratminicola in sorghum have been described
elsewhere (Edmunds et al. 1970; Edmunds and
Zummo 1975; Tarr 1962). Variability in symptoms
may be due to variation in the pathogen,
host resistance, or physiological status of the
host following infection (Frederiksen 1984).
Survival, seasonal persistence, and spread of
inoculum
C. graminicola survives from season to season on
infected crop residues and infected weed hosts
(Tarr 1962). Naylor and Leonard (1977) reported
that G graminicola survived through the winter
and the following growing season in exposed
infected maize stalks in North Carolina. C. graminicola
has been reported to persist for 18 months
as a saprophyte in plant tissue colonized during
parasitism (Vizvary 1975), but conidia or mycelia
in the absence of residue lysed within a few
days (Vizvary and Warren 1982).
A few reports suggest that C. graminicola is
seed transmitted (Tarr 1962). However, seed
transmission was demonstrated by the water
agar seedling symptom test and in a pot experiment
(Basu Chaudhary and Mathur 1979).
C graminicola has been reported to survive on
maize seeds for longer than 1 year (Warren and
Nicholson 1975; Warren 1977). Warren and
Nicholson (1975) reported that seedlings derived
from infected maize seeds usually are
infected.
Primary infection is commonly from the mycelium
and conidia on the crop residue (Dickson
1956). In wet weather, pink masses of spores
ooze from the acervuli and are spread by splashing
rains (Edmunds et al 1970). Nicholson and
Moraes (1980) demonstrated that spores of
C graminicola axe produced in association with
water-soluble mucilaginous matrix (spore matrix)
which protects them against desiccation
and aids in their survival and dissemination.
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They also suggested that spores in the field may
survive and be dispersed in dry particulate matter.
The role of infected seed as a possible source
of primary infection and transmission was demonstrated
(Basu Chaudhary and Mathur 1979).
Infected weed hosts such as Echinochloa colonum,
Digitaria sanguinalis, and Dactyloctenium aegyptum
were reported to act as sources of primary
infection (ICRISAT 1983).
Host range and physiological specialization
C. graminicola has a wide range among cultivated
and wild species of cereals and grasses
(Tarr 1962), including wheat, barley, oats, rye,
maize, sorghum, sudangrass, and johnsongrass
(Bruehl and Dickson 1950; Luke and Seecher
1963; Sanford 1935; Shurtleff 1973; Wiese 1977).
However, isolates from one host do not necessarily
infect other hosts. The capacity of an isolate
of C. graminicola to infect several hosts is not
a subject of general agreement. Some writers report
that an isolate of C. graminicola is capable
of infecting several hosts (Chowdhury 1936;
LeBeau et al. 1951; Lohman and Stokes 1944;
Wheeler et al. 1974), but many others report evidence
of a high degree of host specificity among
isolates of G graminicola (Ali 1986; Bruehl and
Dickson 1950; Dale 1963; Hooker 1977; LeBeau
1950; Pupipat and Mehta 1969; Shahnaz and
Nicholson 1979; Tarr 1962; Williams and Willis
1963; Zwillenberg 1959). Because of this contradicting
information, additional studies to identify
reservoir hosts of C graminicola isolates that
attack sorghum become essential. Crop sequencing,
cultural practices, and breeding for disease
resistance are effective measures of disease control,
but require accurate knowledge of host
specificity.
Pathogen variability
C. graminicola is a highly variable species. Harris
and Johnson (1967) have previously suggested
the existence of races of C. graminicola; and some
soxghum cultivars are reported to react differently
in Texas, Mississippi, and Georgia (Frederiksen
and Rosenow 1971). Harris and Cunfer
(1976) reported shifts in plant reaction to anthracnose
in some cultivars and suggested the
existence of races of C. graminicola. Pastor-Cor-