Sorghum Diseases in India
Sorghum Diseases in India
Sorghum Diseases in India
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<strong>in</strong>icola), head mold (Curvularia lunata), ear blight<br />
(Fusarium heterosporum), leaf spots caused by<br />
Phyllosticta sorghiphila, Mycosphaerella holci, and<br />
Gloeocercospora sorghi, sooty stripe (Ramulispora<br />
sorghi), stalk rots caused by Gibberella fujikuroi,<br />
Macrophom<strong>in</strong>a phaseol<strong>in</strong>a, and Nigrospora oryzae,<br />
and bacterial stripe (Pseudomonas andropogonis)<br />
(Rothwell 1983).<br />
In 1985, the Plant Pathology Advisory Service<br />
at Zimbabwe's Plant Protection Research Institute<br />
reported the first record of long smut<br />
(Tolyposporium enhrenbergii) on sorghum. Viruslike<br />
symptoms, most likely due to maize dwarf<br />
mosaic virus, have been noticed on a number of<br />
l<strong>in</strong>es <strong>in</strong> the SADCC/ICRISAT <strong>Sorghum</strong> Disease<br />
Observation Nursery grown at the Henderson<br />
Research Station, at Mazoe s<strong>in</strong>ce 1985 [as reported<br />
by Mughogho (Obilana 1986)]. Local sorghum<br />
varieties—Red Swazi, Serena, DC 75,<br />
SV 1, and SV 2—grown at research stations<br />
have exhibited similar symptoms. However,<br />
these symptoms have not yet been reported <strong>in</strong><br />
farmers' fields <strong>in</strong> the communal areas.<br />
In pearl millet, ergot (Claviceps fusiformis) and<br />
smut (Tolyposporium penicillariae) are the major<br />
diseases. Downy mildew (Sclerospora gram<strong>in</strong>icola),<br />
zonate leaf spot (Gloeocercospom sp),<br />
leaf spots caused by various fungi (Cochlibolus<br />
bicolor, Colletotrichum sp), rust (Pucc<strong>in</strong>ia penicillariae),<br />
and false mildew (Beniowskia sphaeroidea)<br />
are considered of m<strong>in</strong>or importance.<br />
False mildew is still classified as a m<strong>in</strong>or disease,<br />
because false mildew has not yet been<br />
recorded <strong>in</strong> farmers' fields. But serious epiphytotics<br />
of false mildew have been reported <strong>in</strong><br />
research stations <strong>in</strong> regions II and III (Muza et al.<br />
1986; Mushonga and de Milliano, personal communication).<br />
Screen<strong>in</strong>g work carried out dur<strong>in</strong>g<br />
the 1986/87 season revealed that most of the local<br />
germplasm and our recently released variety,<br />
PMV 1, are susceptible to false mildew and ergot.<br />
Fortunately some sources of resistance to<br />
these diseases are available <strong>in</strong> the global germplasm,<br />
and it may be that these can be <strong>in</strong>corporated<br />
<strong>in</strong> our breed<strong>in</strong>g l<strong>in</strong>es.<br />
Dur<strong>in</strong>g the past 2 years, a new leaf spot of<br />
pearl millet caused by Bipolaris urochloae was recorded<br />
<strong>in</strong> Zimbabwe. Observations on a susceptible<br />
l<strong>in</strong>e, 7042, <strong>in</strong> a disease-monitor<strong>in</strong>g nursery<br />
at Henderson Research Station have clearly <strong>in</strong>dicated<br />
that this leaf spot is a potentially important<br />
disease. L<strong>in</strong>e 7042 succumbed to the disease<br />
before head<strong>in</strong>g.<br />
Yield-loss studies have not yet been carried<br />
out <strong>in</strong> Zimbabwe, but it has been noticed that<br />
losses due to these diseases can be substantial,<br />
especially <strong>in</strong> the higher-ra<strong>in</strong>fall areas (Sanderson<br />
1967, pp. 17-23).<br />
Zimbabwe's Plant Pathology<br />
Research Programs<br />
Our research is ma<strong>in</strong>ly aimed at produc<strong>in</strong>g for<br />
communal farmers of limited resources, cultivars<br />
with stable resistance to the major diseases.<br />
Communal farmers are Zimbabwe's<br />
ma<strong>in</strong> growers of these crops.<br />
The follow<strong>in</strong>g objectives are sought:<br />
1. Development of reliable field-screen<strong>in</strong>g techniques<br />
for major sorghum and pearl millet<br />
diseases.<br />
2. Identification of sources of resistance and <strong>in</strong>corporation<br />
of this resistance by breeders <strong>in</strong>to<br />
genotypes with other desirable characters,<br />
such as high yield and drought tolerance.<br />
3. Determ<strong>in</strong>ation of stability of resistance<br />
through multilocational trials with<strong>in</strong> Zimbabwe<br />
and neighbor<strong>in</strong>g countries.<br />
Develop<strong>in</strong>g reliable screen<strong>in</strong>g<br />
With the help of SADCC/ICRISAT, methods to<br />
establish a 'sick plot' for resistance screen<strong>in</strong>g<br />
aga<strong>in</strong>st sorghum downy mildew were tested<br />
and found to be effective. In the 1st year,<br />
spreader rows were established from artificially<br />
<strong>in</strong>fected seedl<strong>in</strong>gs. In the 2nd year, the ratoon of<br />
the spreader rows was used to <strong>in</strong>fect newlysown<br />
spreader rows and the test sorghums.<br />
Now under test (1987/88) for downy mildew<br />
resistance at SADCC/ICRISAT's Matopos Research<br />
Station are 72 advanced l<strong>in</strong>es and 9 released<br />
varieties. Of the n<strong>in</strong>e released varieties,<br />
SV 1, SV 2, PNR 8311, and PNR 8544 were found<br />
to be resistant with severity scores of 0 to 5%. We<br />
are <strong>in</strong> the process of establish<strong>in</strong>g our own 'sick<br />
plot' at Henderson Research Station, about 30<br />
km northeast of Harare.<br />
Leaf blight <strong>in</strong> sorghum. Epiphytotics of leaf<br />
blight have been successfully created by <strong>in</strong>oculat<strong>in</strong>g<br />
sorghum plants with <strong>in</strong>fected ground<br />
leaves prior to head<strong>in</strong>g. Overhead irrigation was<br />
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