Sorghum Diseases in India

more from disease than did those made in June,
and sowings made during September and the
first fortnight of October (postrainy season) suffered
more disease (Anahosur and Patil 1981a).
Patil et al. (1982) and Mughogho and Pande
(1983, pp. 11-24) reported that increased plant
densities are associated with increased infection.
Effective chemical control techniques for this
disease are not yet available; use of resistant varieties
and hybrids is the most promising approach.
Screening to identify resistant genotypes
presently follows three procedures: the toothpick
method (Hsi 1961), stem tape inoculation
method (Mayee and Garud 1978), and the sick
plot method. The toothpick method, with modifications,
has been followed at different Centers
(Mughogho and Pande 1983, pp. 11-24; Anahosur
1983). The screening procedure is as
follows: in the sick plots, during the second fortnight
of September, two rows of the test
entry are sown between two rows of the susceptible
control (CHS 6) in three replications.
Twenty plants in one of the rows are inoculated
in the second internode with M. phaseolinacoated
tooth picks 15 days after anthesis. Plants
in the other row are exposed to natural infection.
Lodging percentage, number of nodes crossed,
length of spread in the stalk, and differences in
grain mass are recorded and compared. Although
infection success is not always consistent,
this method seems to be the most suitable
available.
Among several genotypes tested, E 36-1 has
shown stable resistance. Tolerant genotypes are
A 1, Afzalpur local, SPV 249, SPV 428, and SPV
488 (Anahosur and Patil 1983a). Breeding charcoal
rot resistant varieties using CSV 5 as the
resistant source produced resistant high-yielding
lines such as SPV 248 and SPV 488 (Gowda
et al. 1981). Testing of lines developed from
crosses SPV 86 x E 36-1 and E 36-1 x SPV 86 is in
progress at Dharwad Centre. Inheritance of resistance
studies revealed that resistance was
partially dominant and controlled by polygenes
and that heritability was poor (Rana et al. 1982a).
Venkatrao and Shinde (1985) reported that susceptibility
was dominant and resistance was
controlled by polygenes and by nonallelic interaction.
Additive x dominance and dominance x
dominance effects predominated in resistance.
The quantity of root and stalk sugars, phenols,
and amino acids in a resistant sorghum (E 36-1)
was more than in a susceptible (CSH 6). Further,
the quantity of sugars and phenols in diseased
root and stalk was considerably less than in
healthy plants of the susceptible genotypes
(Anahosur et al. 1982; Anahosur and Naik 1985).
Fusarium root and stalk rot caused by
Fusarium rnoniliforme and Fusarium moniliforme
var subglutinanse was destructive in postrainy
season in Karnataka (Anahosur et al. 1980a).
During an epiphytotic of F. monilifortne stalk rot
on 16 ha in Bagalkot the loss in grain yield was
15-40% in M 35-1 and Muguthi.
Screening of several varieties by tooth-pick
method in the postrainy season at Dharwad indicated
that CSV 5, SPV-386, 391, and 392 possessed
some resistance.
Downy mildew
AICSIP's sorghum downy mildew work is concentrated
at Dharwad, Mysore, and Coimbatore.
This disease has very high potential for economic
losses. Crop-loss estimates in genotypes
of varying susceptibility in 1985 and 1986 (Table
4) indicated that maximum grain loss (78.6%)
occured in the highly susceptible DMS 652,
whereas the smallest grain loss (2.7%) was seen
in CSV 4. Maximum disease pressure in 1985
was 73.8%. In 1986, the disease pressure was
greater (94.2%) and thus grain loss (93,5%) maximum
in highly susceptible DMS 652 and minimum
(9.6%) in CSV 4. Other genotypes showed
greater losses in yield in 1986 than in 1985.
Table 4. Average loss (%) in grain yield because
of sorghum downy mildew (SDM) in 1985 and
1986.
Genotype
SDM
incidence
(%)
Grain yield
loss
(%)
CSV 4 5.19 6.16
CSV 10 11.42 12.98
SPV 475 37.35 46.47
CSH 5 11.40 18.33
CSH 9 12.78 25.82
SPH 196 18.70 29.73
296 B 50.95 52.83
DMS 652 83.88 86.06
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