Sorghum Diseases in India
Sorghum Diseases in India
Sorghum Diseases in India
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<strong>Sorghum</strong> <strong>Diseases</strong> <strong>in</strong> Western Africa<br />
M.D. Thomas 1<br />
Abstract<br />
In western Africa sorghum (<strong>Sorghum</strong> bicolor) is attacked by several fungi, bacteria, viruses, and<br />
by the parasitic weed Striga hermonthica. <strong>Sorghum</strong> is grown ma<strong>in</strong>ly <strong>in</strong> the Sudanian Zone (500-<br />
1000 mm ra<strong>in</strong>fall) and <strong>in</strong> the northern Gu<strong>in</strong>ean Zone (1000-1200 mm ra<strong>in</strong>fall). Some sorghum is<br />
also grown <strong>in</strong> the Sahelian Zone (400-500 mm ra<strong>in</strong>fall). The importance of any of the sorghum<br />
diseases depends to a large extent on the zone <strong>in</strong> which the crop is grown. In local and <strong>in</strong>troduced<br />
genotypes alike, diseases such as gray leaf spot and leaf anthracnose are more prevalent <strong>in</strong> the<br />
northern Gu<strong>in</strong>ean and Sudanian zones; sooty stripe and long smut occur more frequently <strong>in</strong> the<br />
Sudanian Zone. Gra<strong>in</strong> mold is found mostly <strong>in</strong> <strong>in</strong>troduced genotypes which mature dur<strong>in</strong>g periods<br />
of relatively high ra<strong>in</strong>fall. Oval leaf spot, zonate leaf spot, leaf blight, head smut, and covered smut<br />
occur at low levels <strong>in</strong> both the northern Gu<strong>in</strong>ean and Sudanian Zones. Head smut is a particular<br />
problem <strong>in</strong> farmers' fields. Striga hermonthica occurs abundantly <strong>in</strong> all zones and attacks all<br />
genotypes. Prelim<strong>in</strong>ary data <strong>in</strong>dicate that symptoms of gray leaf spot first appear between flower<strong>in</strong>g<br />
and 10 days after <strong>in</strong> Burk<strong>in</strong>a Faso. The progress of the disease is slow and exceeds 75% leaf area<br />
<strong>in</strong>fected only at maturity. In contrast, symptoms of leaf anthracnose appear early, the disease<br />
progresses rapidly, and kills top leaves dur<strong>in</strong>g gra<strong>in</strong> formation. Soil shad<strong>in</strong>g with groundnut<br />
suppressed Striga <strong>in</strong> farmers' fields.<br />
Introduction<br />
<strong>Sorghum</strong> [<strong>Sorghum</strong> bicolor (L) Moench] is grown<br />
widely <strong>in</strong> many countries <strong>in</strong> semi-arid western<br />
Africa. In several of these countries, sorghum<br />
can be regarded either as the staple food or the<br />
second most important source of energy for the<br />
population. Most of the sorghum is grown <strong>in</strong> the<br />
Sudanian Zone (500-1000 mm ra<strong>in</strong>fall) and the<br />
northern Gu<strong>in</strong>ean Zone (1000-1200 mm ra<strong>in</strong>fall).<br />
Some sorghum is also grown <strong>in</strong> the southern<br />
Sahelian Zone (400-500 mm ra<strong>in</strong>fall).<br />
In western Africa sorghum is attacked by<br />
several fungi, bacteria, viruses, and the parasitic<br />
weed Striga hermonthica (Del.) Benth (Table 1).<br />
The situation with nematodes is not quite clear<br />
and there appears to be no report of nematode<br />
<strong>in</strong>fection of sorghum <strong>in</strong> western Africa. There is<br />
variation <strong>in</strong> <strong>in</strong>cidence and severity of the dis<br />
1. Pr<strong>in</strong>cipal <strong>Sorghum</strong> Pathologist, ICRISAT. B.P, 910, Bobo-Dioulasso, Burk<strong>in</strong>a Faso.<br />
eases accord<strong>in</strong>g to the agroecological zones<br />
mentioned above. Thus, the importance of any<br />
one of the sorghum diseases <strong>in</strong> western Africa<br />
depends to a large extent on the zone where<br />
the crop is grow<strong>in</strong>g. Importance is also related<br />
to whether a disease occurs on local landraces<br />
or on <strong>in</strong>troduced genotypes. There appears to<br />
be "pockets" with<strong>in</strong> western Africa for the<br />
occurrence of some diseases. For example,<br />
symptoms of downy mildew and virus-like<br />
symptoms have been reported <strong>in</strong> some countries<br />
(Tyagi 1980, Zummo 1984), whereas <strong>in</strong><br />
many countries these two categories of symptoms<br />
are absent, or at least have not been reported.<br />
In general the importance of a disease<br />
is related to several other factors, such as the<br />
progress of the disease dur<strong>in</strong>g the different<br />
growth stages of the host and the effect of the<br />
disease on gra<strong>in</strong> yield.<br />
Thomas, M.D. 1992. <strong>Sorghum</strong> diseases <strong>in</strong> western Africa. Pages 25-29 <strong>in</strong> <strong>Sorghum</strong> and millets diseases: a second world review,<br />
(de Milliano, W.A.J., Frederiksen, R.A., and Bengston, G.D., eds). Patancheru, A.P. 502 324, <strong>India</strong>; International Crops Research<br />
Institute for the Semi-Arid Tropics. (CP 733).<br />
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