Sorghum Diseases in India

millet lines and cultivars from national programs
in western African and from ICRISAT's
Sahelian Center are tested for stability of DM
resistance. In 1986, cultivars from four national
programs were sent for testing to sites in five
countries in western Africa (ICRISAT 1986).
Economic resources of the Sahelian farmer are
very limited, and chemical control of DM is nonaffordable.
The most practical means of control of
S. graminicola in Sahelian farmers' fields will be
crop varieties resistant to or with relatively low
levels of susceptibility to downy mildew.
Panicle Diseases
The two main panicle diseases of pearl millet are
smut (Tolyposporium penicillariae Bret.) and ergot
(Claviceps fusifonnis Loveless). In smut infections,
some grains, in the head are replaced by
green smut sori that eventually turn dark brown
and break off, releasing balls of teliospores.
Highest smut severity usually occurs on heads
with poor exertion. That part of the head covered
by the flag leaf is often ideal for the development
of the smut fungus.
Smut is found in all millet-growing areas of
western Africa, but yield losses are of less importance
than those caused by downy mildew.
Selvaraj (1979) estimated yield losses of 2-3%
due to smut in Nigeria. In late-sown millet at
Bengou, Niger, boot-leaf stage coincided with
high and well-distributed rainfall and high humidity
contributing to much higher smut incidence
on BJ 104 (Table 3).
Table 3. Influence of sowing date on smut
(Tolyposporium penicillarie) severity at INRAN
station, Bengou, Niger, rainy season 1987.
Date of
sowing 1
15Jun
24Jun
6 Jul
18 Jul
Smut
severity 2 (%)
20 (99) 3
40(89)
67 (46)
40(50)
Date of leafboot
stage
21 Jul
3 Aug
18 Aug
29 Aug
1. On sowing date, 10 rows sown in a nonreplicated
plot
2. Based on a scale of 0 to 100%, where 0 = no symptoms,
and 100 = totally covered.
3. Number of plants scored is indicated in
parentheses.
Some breeding materials and certain varieties
showing resistance in India also show resistance
in western Africa. A large number of
varieties and lines of western African origin
were found to have resistance or at least the ability
to endure infection.
Yield losses in pearl millet due to ergot are of
minor importance in western Africa (Selvaraj
1980), but can be devastating on short-duration
photoperiod-insensitive cultivars. Observations
in farmers' fields in the north of Cameroon
showed only 3% ergot severity (IRA/ICRISAT
1987). The sclerotia of this pathogen contain alkaloids
that can be hazardous if eaten.
Leaf Diseases
Leaf diseases, although currently less important
than DM, are potentially damaging in western
Africa. Leaf blast and rectangular leaf spot can
be found in nearly all millet-growing areas of
western Africa, whereas circular leaf spot (Dactuliophora
elongata) is found only in the high rainfall
zones (600 mm). Circular leaf spot appears
as concentric or zonate spots studded with black
sclerotia (Tyagi 1985).
Rust (Puccinia penniseti) is rarely found in the
Sahelian region. It is mainly observed in zones
with 800 mm rainfall. The fungus appears very
late in the season and usually has little influence
on yield (Girard and Delassus 1978). In some
wetter parts of Nigeria (e.g., the Guinea Savannah)
rust can have some effect on yield.
Phoma leaf spot (Phoma sorghina = Phyllosticta
penicillariae), described by Saccas (1954), appears
in areas with higher rainfall.
A midrib infection on millet in Nigeria, was
identified as Curvularia eragrostidis (Bindawa
1988). Placosphaeria sp (Jouan and Delassus
1971), another leaf disease found rarely on millet,
was observed in Gongola state, Nigeria, in
1986.
Bacterial leaf streak has been described as
Pseudomonas sp whereas bacterial streak symptoms
on samples from Niger have been identified
as Xanthomonas sp. The symptoms of this
bacterial disease look very similar to those reported
on proso millet (Elliott 1923). Bacterial
disease on pearl millet was reported (Zummo
1976) as yellow leaf blotch (Pseudomonas sp).
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