Sorghum Diseases in India

Nematode Pathogens of Sorghum
J.L. Starr 1
Abstract
Plant-parasitic nematodes have only recently received recognition as pathogens of sorghum. The
impact of nematodes on sorghum yield potential relative to other pest groups, however, is poorly
documented. Growth suppression and sorghum yield loss due to nematode parasitism has been
documented for nine species of nematodes in seven genera; an additional 22 species are known to
parasitize sorghum. The associations of nematodes with sorghum are reviewed and emphases
suggested for future research.
Introduction
Plant-parasitic nematodes are ubiquitous in environments
that support vascular plants. All
plant species examined to date are hosts (support
nematode development and reproduction)
to one or more species of nematodes. Similarly,
nearly every plant species studied has been
shown to suffer damage from the feeding activities
of nematode parasites. However, not all
nematodes parasitic (able to reproduce) on a
given host are pathogenic (able to cause disease
and suppress growth) to that host. Despite the
universal occurrence of plant-parasitic nematodes,
they are still frequently considered not to
be of major importance for many crop species.
Until recently sorghum was not considered to
suffer significant damage due to plant-parasitic
nematodes. Evidence documenting the host status
of sorghum to numerous nematode species is
accumulating; many of these nematodes are also
pathogenic. Evidence of parasitism and pathogenicity
by different nematode species on sorghum
is reviewed.
Sedentary Endo- and Semiendo-
Parasites
Eight species from four genera of sedentary
nematodes with endo or serniendo feeding
habits have been shown to be parasitic on sorghum
(Table 1). Pathogenicity, however, has
been demonstrated for only one species. Meloidogyne
incognita suppressed dry weight accumulation
of sorghum in greenhouse tests by
15%, field-test yields were suppressed by 33%
(Orr 1967). Similarly, Thomas and Murray (1987)
observed significant yield increases when field
microplots infested with M. incognita at 490 eggs
500 cm -3 soil were treated with 1,3-dichloropropene
or aldicarb.
Data on pathogenicity are lacking for the
other Meloidogyne spp known to parasitize sorghum.
It is known, however, that only selected
populations of M. naasi are able to parasitize sorghum.
Mitchell et al. (1973) separated M. naasi
into five races based on differential parasitism of
four indicator hosts, race 5 populations reproduced
on sorghum.
1. Associate Professor, Department of Plant Pathology and Microbiology, Texas Agricultural Experminent Station, College Station,
TX77843 USA.
Starr, J.L., 1992. Nematode pathogens of sorghum. Pages 179-185 in Sorghum and millets diseases: a second world review, (de
Milliano, W.A.J,, Frederiksen, R.A., and Bengston, G.D., eds). Patancheru, A.P. 502 324, India: International Crops Research Institute
for the Semi-Arid Tropics.
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