Sorghum Diseases in India

ported significant growth suppression of sorghum
in response to populations of Tylenchorhynchus
nudus of ca. 400 individuals 100 cm" 3 of
soil in greenhouse tests. Furthermore, he noted
that the effects of the nematode were greater
under conditions of low versus high soil fertility.
Tylenchorhynchus martini suppressed yield of sorghum
at populations of 2000 to 5000 individuals
250 cm -3 of soil in field tests (Hafez and Claflin
1982) but not at initial populations of 750 to 1750
individuals 250 cm* 3 soil (Todd and Claflin
1984). In both tests T. martini did reproduce on
sorghum. Cuarezam-Teran and Trevathan (1985)
reported that the stunt nematode Quinisulcius
acutus caused significant root pruning and root
necrosis (Fig. 2) and was thus parasitic and
pathogenic on sorghum in greenhouse tests.
They also examined the combined effects of
Q. acutus and P. zeae on sorghum; the combined
affects of the two species were less than additive.
Their experimental design, however, was
inadequate to determine if a true negative (antagonistic)
interaction occurred.
Of the ring nematodes, to date only Criconemella
sphaerocephala has been shown to be
pathogenic to sorghum. Kinlock (1987) reported
a significant negative linear correlation between
initial populations of C. sphaerocephala and sorghum
height and grain yield in field tests. In
these studies initial populations of approximately
300 nematodes 100 cm -3 of soil were required
to cause a 10% yield loss.
Among the Adenophora two species have
been shown to be pathogenic to sorghum. In
greenhouse tests, Trichodorus allius at 125 individuals
100 cm -3 of soil suppressed growth of
sorghum at 15-25°C but not at 10°C or 30-35°C
(Smolik 1977). Longidorus africanus, at populations
as low as 50 nematodes 500 cm -3 of soil,
suppressed sorghum growth in greenhouse tests
(Lamberti 1969). After 10 weeks populations had
increased to as many as 750 L. africanus 500 cm- 3
Figure 2. Root symptoms of Quinisulcius acutus on sorghum. A: noninoculated control. B:
inoculated with 1000 nematodes L -1 of soil.
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