Sorghum Diseases in India

een observed, the disease is potentially dangerous
to sorghums in the tropical areas.
Bacterial stripe. (Pseudomonas andropogonis.)
The distribution and incidence of this disease is
similar to that of bacterial streak, but Pseudomonas
is less common than Xanthomonas at
Guanajuato. On the other hand, there are reports
that indicate a wide distribution of Pseudomonas
in the high valleys of Jalisco and the Ocotlan
area. Incidence, however, varies from year to
year, and the disease is so far without economic
importance
Sooty strip. (Ramulispora sorghi.) It is sometimes
found in Tamaulipas, Jalisco, and small
areas of the tropics in Mexico. The incidence of
this disease is very low and is at present of little
importance.
Bacterial sun spot. (Pseudomonas sp.) It is similar
in importance and distribution to sooty
stripe.
Rust. (Puccinia purpurea Cooke.) It is very common
in tropical and subtropical areas of Mexico,
particularly at the Jalisco area and in southern
Tamaulipas; it can be very high in incidence and
economic importance. Commercial hybrids have
been severely affected in the last 5 years, with
scores of 5 on a 1 to 5 severity scale. The damage,
however, is not as high as expected, as the
pathogen appears after flowering. Most commercial
hybrids are susceptible to the pathogen.
Tolerant hybrids, however, are extensively sown
in areas such as Ocotlan in Jalisco.
Studies on the chemical control of rust have
evaluated chlorothalonil (Bravo 500 ® ), three
sprayings—1 kg a.i. ha -1 applied prior to flowering,
at flowering, and 15 days following—
(Betancourt and Narro 1983; Frederiksen et al.
1983; Rodriguez 1983). Even though the incidence
of pustules was reduced on the fungicidetreated
plants, there is evidence that suggests
that rust is not correlated with yield, although
the presence of rust was correlated with the
presence of Fusarium.
Smuts
Three types of smuts are present in Mexico: covered
kernel, loose kernel, and head smut
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Head smut. (Sporisorium reilianum.) This is the
only smut of economic importance in Mexico. It
is found in most of the country's sorghum-growing
areas, particularly in northern Tamaulipas
where incidences up to 40% in commercial hybrids
have been reported (Aguirre 1984a). The
pathogen is highly variable and several races
have been reported. In Tamaulipas, races 1, 2, 3,
and 4 occur (Aguirre 1986). In Jalisco, Michoacan,
and Guanajuato races 1, 2, and 3, (Hernandez
et al. 1983) are common, races 1 and 3,
however, are the most common with incidences
from 20 to 40%. Herrera and Betancourt (1986)
reported that race 3 of the pathogen is the most
widely distributed in Mexico.
Control of head smut has been achieved by
planting resistant hybrids such as RB 3030, RB
3006, and BJ 83 from INIFAP and others from
private companies. Since the hybrids are also
resistant to downy mildew, two pathological
problems are solved simultaneously.
In Tamaulipas, a program for resistance to
head smut and downy mildew was reinforced in
1977, with the objective of obtaining hybrids resistant
to both pathogens. In 1984, several genotypes
with high levels of resistance were
identified; so far, the resistance to head smut and
downy mildew has been stable (Aguirre 1986).
Root and Stalk Rots
Stalk rot and head blight. (Fusarium moniliforme
Sheldon.) These are diseases widely distributed
in Mexico and are economically
important in the states of Jalisco, Guanajuato,
and Michoacan. Most commercial hybrids are
susceptible, though a few have shown moderate
tolerance. At Guanajuato, incidences up to 40%,
with scores of 4 on a 1 to 5 scale, have been
reported (Narro and Betancourt 1983).
The effect of this disease on yield was estimated
by noting yields of inbred and hybrid
plants inoculated at the boot stage, anthesis, and
15 days after anthesis. Yield reductions were 33,
11, and 8%, respectively. In the case of the hybrids,
when both parental lines were tolerant the
yield reduction was 14% whereas in susceptible
lines yield reduction accounted for 30% when
plants were inoculated at the boot stage (Hernandez
et al 1987a).
In histopathological studies it was found that
RTx 430, rated as tolerant, contains more lignin