Sorghum Diseases in India

intermediate population had 22.5% SDM incidence
and yielded 1 t ha -1 . The susceptible population
had 42.9% SDM incidence, yielding only
0.8 t ha -1 ,44.3% less than the resistant population.
Evaluation of Sorghum Cultivars for
Resistance
For the farmer, sowing disease-resistant material
is the most cost-efficient way of reducing losses
due to diseases (Mundt and Browning 1985).
Most of the sorghum in the Honduras is produced
by resource-poor farmers, so it is desirable
to have sources of disease resistance in the Honduras
identified, so that these traits can be incorporated
into future sorghum varieties and hybrids.
International disease nurseries are an excellent
source of disease-resistant cultivars. These
nurseries are generally put together with the
most outstanding sources of resistance for a variety
of diseases. Many such disease nurseries
are available, and several were sown at two locations
in 1983 and 1984 in the Honduras. They
were evaluated for disease resistance to naturally
occurring diseases during these growing
seasons. Other nurseries, sown by researchers
working with the Honduran sorghum project,
were also evaluated to identify possible sources
of disease resistance which later may be used in
the sorghum improvement program there.
Cultivars that show disease resistance in a
number of locations are likely to be more stable
than those having specific types of resistance,
which may be resistant at one site but susceptible
at another (Wiese 1980). Different specific resistances
can also be used in combination (Mundt
and Browning 1985). The basis of any gene-deployment
scheme is to have known resistance of
different types. A lesson to be learned from the
past is avoiding the use of only one source of
specific resistance. Selection of cultivars to be
used as sources of resistance should be based on
several trials through time and space, preferably
tested in the areas of anticipated sowing.
Results and discussion
Resistance was found for AW, SDM, and gray,
ladder, oval, and zonate leaf spot diseases.
Among the landraces, resistance was identified
for SDM, gray leaf spot, ladder spot, and oval
leaf spot. Eighteen sorghum entries, including
improved lines and landraces, were found to
possess resistance to two or more diseases (Table
6).
As more testing is done, information available
regarding the stability of these resistant
sources will become more reliable. If possible,
diverse sources of resistance must be used to
safeguard against rapid "breakdown" to a given
disease.
The stable source of resistance should be put
into a uniform nursery along with experimental
materials. This permits the constant monitoring
of the elite resistant sources, at the same time
facilitating direct comparison of experimental
materials with elite lines. Cultivars, particularly
those also well adapted to climatic conditions in
the Honduras, with resistance to more than one
disease should prove useful in saving valuable
breeding time.
Table 6. Sorghum entries selected for resistance
to several diseases from various nurseries
in the Honduras 1983-85.
Cultivar/designation/
entry Disease resistance 1
SC 326-6 AC,GR,LD,ZN(AN)
82 CS 447 AC,GR,LD,ZN
80 B 2892 GR,LD,ZN
R 3338 GR,LD,ZN
82 EON 112 AC,SDM,ZN
San Miguel 1 GR,LD,OV
SC 748-5 GR, ZN (AN)
77 CS1 GR,LD
79 HW 207 AC,ZN
Tx 435 AC, SDM
Tx 2794 LD,SDM
81 B 6078 LD,SDM
Pom Pom GR, LD
Las Lajas GR,LD
VG146 GR, SDM
82 BH 5718 SDM,ZN
81 EON 69 AC,ZN
Brandes ZN(AN)
1. AC = Acremonium wilt, GR - Gray leaf spot, LD =
Ladder spot, (AN) = Reported resistant to anthracnose
elsewhere, OV = Oval leaf spot, SDM = Sorghum
downy mildew, ZN = Zonate leaf spot
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