Sorghum Diseases in India

ported in 1977 (Martinez 1984). In 1981, field
samples were collected and inoculations were
made in one replication of the International
Virus Disease Nursery (IVDN) and MDMV confirmed
(Narro and Hernandez 1984). In 1982, the
MDMV was identified by using the IVDN in the
Jalisco area.
Toler (1980) points out that only strains A and
B of the MDMV are important. Strain A infects
johnsongrass; strain B does not. A study to determine
the distribution of strains A and B of
MDMV indicated that only strain A was present
in Mexico.
Different sowing dates at the Experimental
Station at the Bajio were used to study the distribution
of this virus in relation to sowing date. It
was observed that 35% of incidence occurred
between 15 March and 15 April, with a significant
reduction in later sowings (Narro and Delgadillo
1985). At the present time an evaluation
of yield reduction caused by MDMV (A and B)
is underway with four genotypes. In relation
with genetic resistance, the best 25 inbreds of
Bajio program were evaluated; 8 lines showed
resistance to strain A, 15 to strain B, and 5 to
both strains; the inheritance of resistance to
MDMV is now being studied by using germplasm
with different reaction to the virus.
Foliar Diseases
Leaf blight. (Exserohilum turcicum Pass.) It is
causing severe damage, mainly in the states of
Jalisco, Michoacan, and Guanajuato, but it is also
present in seven other states.
In Jalisco it is very common to find commercial
fields, rainfed and irrigated alike, highly
damaged by the pathogen if sown late in the
season (Distancia and Betancourt 1984). At La
Barca (State of Jalisco), incidences up to 80%
were found in susceptible hybrids, and few hybrids
show tolerance.
Studies on chemical control of leaf blight
show that preventive treatment with fungicides,
such as maneb, propiconazole (Tilt ® ), or zineb,
are not effective. In 1981, the germplasm developed
at the Bajio was evaluated in three locations
with high incidence of the pathogen; only
one inbred (E. 13B, a kafir derivative) was resistant;
in general, all kafir derivatives from
BTx 3197 have shown tolerance.
Introduced material (ATx 623 x SC 0326-6
and ATx 623 x R 6956) that allowed identification
of two restorer lines with good levels of
resistance were identified in the TAT (Tropical
Adaptation Test). As BTx 623 is susceptible, it is
concluded that dominance is present in both
pollinators. It should be mentioned that INIFAP
has an experimental station at Ocotlan, Jalisco
(near La Barca) where a breeding program for
resistance to foliar diseases has been in place
since 1980. Workers there have obtained the second
backcross in a group of foliar resistant B
lines; these are now being sterilized. Crosses of
inbreds from Bajio x Texas have shown better
response than those of Texas x Texas. Excellent
sources for leaf-disease resistance have been developed
by this program.
Bacterial streak. (Xanthomonas campestris pv
holcicola.) This occurs in most of the Bajio area; at
the state of Guanajuato its incidence is very
high, mainly on susceptible genotypes such as
Tx 623 (ratings of 4 on a 1 to 5 scale). Data on the
effects of this disease on yield are not available.
It probably combines with other diseases to predispose
the sorghum plants to infection by
others, such as Fusarium moniliforme. A nursery
from Texas A&M Univeristy, established in 1983,
contains seven lines with tolerance to this pathogen.
These lines will be useful in the future as
sources of resistance to foliar pathogens.
Zonate leaf spot.(Gloeocercospora sorghi.) It is
widely distributed, mainly in the subtropical
areas of Tamaulipas, the Ameca area in Jalisco,
and coastal areas of Veracruz and Chiapas. Economic
losses related with this disease have not
been reported, however.
Gray leaf spot or angular leaf spot. (Cercospora
sorghi.) It is found in almost every sorghum-growing
area of Mexico, but has little
effect on yield because it usually does not infect
the leaves until late in the grain-filling stage,
when the grain is near physiological maturity.
Leaf anthracnose. (Colletotrichum graminicola.)
It has limited distribution in the major sorghumgrowing
areas of Mexico, but is more common in
tropical areas where the sorghum hectarages are
rather small. It is found in northern Tamaulipas
and the coastal areas of Nayarit, Jalisco, and similar
areas. Even though severe damage has not
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