Sorghum Diseases in India

inicola), head mold (Curvularia lunata), ear blight
(Fusarium heterosporum), leaf spots caused by
Phyllosticta sorghiphila, Mycosphaerella holci, and
Gloeocercospora sorghi, sooty stripe (Ramulispora
sorghi), stalk rots caused by Gibberella fujikuroi,
Macrophomina phaseolina, and Nigrospora oryzae,
and bacterial stripe (Pseudomonas andropogonis)
(Rothwell 1983).
In 1985, the Plant Pathology Advisory Service
at Zimbabwe's Plant Protection Research Institute
reported the first record of long smut
(Tolyposporium enhrenbergii) on sorghum. Viruslike
symptoms, most likely due to maize dwarf
mosaic virus, have been noticed on a number of
lines in the SADCC/ICRISAT Sorghum Disease
Observation Nursery grown at the Henderson
Research Station, at Mazoe since 1985 [as reported
by Mughogho (Obilana 1986)]. Local sorghum
varieties—Red Swazi, Serena, DC 75,
SV 1, and SV 2—grown at research stations
have exhibited similar symptoms. However,
these symptoms have not yet been reported in
farmers' fields in the communal areas.
In pearl millet, ergot (Claviceps fusiformis) and
smut (Tolyposporium penicillariae) are the major
diseases. Downy mildew (Sclerospora graminicola),
zonate leaf spot (Gloeocercospom sp),
leaf spots caused by various fungi (Cochlibolus
bicolor, Colletotrichum sp), rust (Puccinia penicillariae),
and false mildew (Beniowskia sphaeroidea)
are considered of minor importance.
False mildew is still classified as a minor disease,
because false mildew has not yet been
recorded in farmers' fields. But serious epiphytotics
of false mildew have been reported in
research stations in regions II and III (Muza et al.
1986; Mushonga and de Milliano, personal communication).
Screening work carried out during
the 1986/87 season revealed that most of the local
germplasm and our recently released variety,
PMV 1, are susceptible to false mildew and ergot.
Fortunately some sources of resistance to
these diseases are available in the global germplasm,
and it may be that these can be incorporated
in our breeding lines.
During the past 2 years, a new leaf spot of
pearl millet caused by Bipolaris urochloae was recorded
in Zimbabwe. Observations on a susceptible
line, 7042, in a disease-monitoring nursery
at Henderson Research Station have clearly indicated
that this leaf spot is a potentially important
disease. Line 7042 succumbed to the disease
before heading.
Yield-loss studies have not yet been carried
out in Zimbabwe, but it has been noticed that
losses due to these diseases can be substantial,
especially in the higher-rainfall areas (Sanderson
1967, pp. 17-23).
Zimbabwe's Plant Pathology
Research Programs
Our research is mainly aimed at producing for
communal farmers of limited resources, cultivars
with stable resistance to the major diseases.
Communal farmers are Zimbabwe's
main growers of these crops.
The following objectives are sought:
1. Development of reliable field-screening techniques
for major sorghum and pearl millet
diseases.
2. Identification of sources of resistance and incorporation
of this resistance by breeders into
genotypes with other desirable characters,
such as high yield and drought tolerance.
3. Determination of stability of resistance
through multilocational trials within Zimbabwe
and neighboring countries.
Developing reliable screening
With the help of SADCC/ICRISAT, methods to
establish a 'sick plot' for resistance screening
against sorghum downy mildew were tested
and found to be effective. In the 1st year,
spreader rows were established from artificially
infected seedlings. In the 2nd year, the ratoon of
the spreader rows was used to infect newlysown
spreader rows and the test sorghums.
Now under test (1987/88) for downy mildew
resistance at SADCC/ICRISAT's Matopos Research
Station are 72 advanced lines and 9 released
varieties. Of the nine released varieties,
SV 1, SV 2, PNR 8311, and PNR 8544 were found
to be resistant with severity scores of 0 to 5%. We
are in the process of establishing our own 'sick
plot' at Henderson Research Station, about 30
km northeast of Harare.
Leaf blight in sorghum. Epiphytotics of leaf
blight have been successfully created by inoculating
sorghum plants with infected ground
leaves prior to heading. Overhead irrigation was
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