Sorghum Diseases in India

Sorghum Smuts
El Hilu Omer 1 and R.A. Frederiksen 2
Abstract
The four smuts of sorghum are reviewed in respect to their economic importance, biology, and
control The two kernel smuts (Sporisorium sorghi and Sphacelotheca cruenta) have been
reduced to minor importance because of seed treatment with fungicides, whereas head smut
(Sporisorium reilianum) and long smut (Tolyposporium ehrenbergii) continue to be significant.
Resistance to long smut has been developed and work on identifying sources of resistance is
underway. Programs to reduce head smut in endemic areas have changed little over the past
decade.
Introduction
Four fungi cause four different smuts in sorghum.
The pathogens Sporisorium reilianum (Kiihn) Langdon
and Fullerton, Sporisorium sorghi (Ehrenberg)
Link, Sphacelotheca cruenta (Kiihn) Potter
and Tolyposporium ehrenbergii (Kiihn) Patouillard
cause head, covered kernel, loose kernel, and
long smut, respectively (Table 1).
Head Smut
The life cycle of head smut (Fig. 1) has been recognized
for some time. The fungus is seedling-infecting
from soilborne teliospores. Teliospores
survive for many years in the field. In Texas, these
spores are estimated to survive up to a decade in
soil. Spores germinate by the production of a
promycelium (epibasidium). On artificial media
these structures produce sporidia. The function or
role of sporidia under natural conditions remains
unknown. Similarly the nuclear condition of the
vegetative and sexual stages of the fungus has
not been elucidated,although the parasitic mycelium
is dikaryotic (Natural 1983). Colonization
of the host following initial penetration and formation
of the sorus has been studied in sorghum
by Wilson and Frederiksen (1970a, 1970b), and
Natural (1983). The process of colonization
appears to be similar in sorghum and maize.
Mycelium of the pathogen grows toward differentiating
meristem, where it grows systemically
with the host. When differentiation begins in the
host, the smut fungus also organizes its sorus
within the host The fungus differentiates into
sporogenous hyphae, cells that ultimately produce
spores and spore balls; partitioning hyphae,
mycelium that grows within the sorus among the
sporogenous hyphae and nonsporogenous hyphae
for all other hyphae in the sorus. Some of
the nonsporogenous hyphae, along with two or
three cell layers of host cells form the peridium.
As the sorus matures and dries, the peridium
ruptures and releases spores that fall to the soil
for the next cycle. As the sorus continues to release
spores, the vascular strands of the host remain.
There are a wide range of symptoms for
sorghum head smut, based in part on the time
and extent of colonization and the length of time
after maturity that the diseased plant survives
(Wilson and Frederiksen 1970a).
1. Plant Pathologist, Agricultural Research Corporation, Gezira Agricultural Research Station, Wed Medani, Sudan.
2. Professor, Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA.
El Hilu Omer and Frederiksen, R.A. 1992. Sorghum smuts. Pages 245-252 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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