Sorghum Diseases in India

ales and Frederiksen (1979) reported that many
of the resistant sorghum entries in Georgia were
susceptible in Brazil; but Redlan, a traditionally
susceptible entry in Georgia, was resistant in
Brazil, Nakamura (1982) identified five races of
C. graminicola using seven differential sorghum
cultivars (Tx 2536, Martin, TAM 428, Tx 430,
Brandes, SC 170-6-17, SC 175-14). Ferreira and
Casela (1986) identified seven races of C graminicola
using 13 differential cultivars of sorghum
(Tx 2536, Martin, TAM 428, Tx 430, Brandes, SC
170-6-17, SC 175-14, SC 112-14, Theis, Reis, Redlan,
SC 326-6, and SC 283). The seven isolates
used in their study were collected from different
locations in Brazil. Ali and Warren (1987) identified
three races of C. graminicola using six differential
cultivars (IS 4225, IS 8361, 954130, 954062,
Br 64, and 954206). The three races were identified
from nine isolates of G graminicola obtained
from Florida, Georgia, Puerto Rico, and Indiana.
They also reported the different races even
among isolates from the same area. The existence
of races among pathogen populations present
challenging problems to breeders and
pathologists trying to develop resistant cvs.
Casela and Ferreira (In press) have proposed
a system of nomenclature of races of C. graminicola
in Brazil. In this system, three sorghum
cultivars (Redlan, SC 326-6, SC 283) are used to
separate eight groups of races, then sorghum
cultivars Tx 623, Brandes, SC 112-14, Martin, Tx
2536, and Theis are used to distinguish 32 races
within each group.
Economic importance
Sorghum anthracnose may limit grain sorghum
production in the humid southeastern USA
(Harris et al. 1964; Harris and Sowell 1970), Latin
America, Brazil, and Venezuela (Pastor-Corrales
and Frederiksen 1979), and other humid tropical
and subtropical areas (Bergquist 1973; Powell et
al. 1977).
Losses in grain yield were estimated to exceed
50% on susceptible sorghum cultivars in a
severe anthracnose epiphytotic in Georgia
(Harris et al. 1964). They reported a negative (r =
-0.632) and highly significant (P = 0.01) correlation
between grain yield and leaf anthracnose
rating. Highly significant (P = 0.01) negative correlations
between grain yield and leaf, head, and
stalk anthracnose ratings were reported. In these
studies, leaf anthracnose and stalk rot were independent
of each other, but the head infection
was associated with both the leaf and stalk
phases of the disease. Powell et al. (1977) reported
that grain yield was reduced by 70% and
more than half the yield loss resulted from incomplete
grain fill as verified by 42% decrease in
1000-seed mass and 17.2% decrease in seed density.
Early seed abortion's role in yield reduction
was also suggested to be important. Gorbet
(1977) reported that grain production of susceptible
sorghum cultivars is severely limited when
the disease develops during heading or early
grain filling. Correlation coefficients between
anthracnose severity and grain yield in 42 sorghum
hybrids were negative and highly significant
for all disease rating dates; however, the r 2
values decreased as grain developed from the
milk stage to harvest (Harris and Fisher 1974).
The percentage loss in sorghum grain yield varied
from 1.2 to 16.4, depending upon anthracnose
severity (Mishra and Siradhana 1979).
Luttrel (1950) reported that serious yield losses
may not occur if leaf symptoms do not appear
until after the plants mature. Ali et al. (1987)
reported that highly significant (P = 0.01) positive
correlations between percentage loss in
grain yield and anthracnose leaf blight (ALB)
severity index occurred in 1984 and 1985 and for
the pooled data of both years, with correlation
coefficients of 0.86, 0.84, and 0.85, respectively.
Correlations between percentage loss in 1000seed
mass and ALB severity also were highly
significant (P = 0.01) for the individual and
pooled data of both years. The highly significant
(P = 0.01) positive correlations between percentage
loss in grain yield and percentage loss in
1000-seed mass indicate that ALB reduces grain
yield of sorghum largely by decreasing seed
mass. They also reported a loss in grain yield of
about 30% in the most-susceptible sorghum cultivar.
They suggested that the amount of loss in
grain yield due to ALB was influenced by the
aggressiveness of the pathogen, sorghum genotype,
and environmental conditions favoring
anthracnose development.
The extent of damage of loss due to anthracnose
stalk rot has been reported as a reflection of
the host susceptibility, environment, aggressiveness
of the pathogen, and physiological status of
the host (Frederiksen 1984).
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