Sorghum Diseases in India

Mughogho: The literature contains no information
on this, and I know of no research program
in this important area.
Mantle: Commenting partly in response to the
previous question on variability in the expression
of ergot sclerotium formation on sorghum,
it is assumed that the review aspect of Dr
Mughogho's paper has been a synthesis of the
sparse literature concerning both India and Africa.
If so, from the experience of our comparative
studies in London on ergot isolates form
India and Africa, and taking into account Dr
Boon-Long's conference report concerning sorghum
pathology in Thailand, it seems probable
that there are some significant geographic differences
in the pathogen. In Thailand, sclerotial
differentiation is absent or slight, while in Africa
sclerotia are frequently produced and are
of a size roughly comparable to that of seed. In
contrast, the Indian spur-like parasitic bodies
produced during the dry season consist mainly
of a distal portion which is actually sphacelial
tissue. Only the lesser proximal portion is a
true sclerotium. The shorter parasitic body produced
during the rainly season may simply be
the sclerotial component, the sphacelial tissue
having been washed away by rain.
Vidyabhushanam: Is there any evidence to indicate
that the seed obtained from ergot-infested
(with honeydew only) heads carrying the
honeydew initiate disease in the next
generation?
Mughogho: There is no information in the literature
on this. However, I would not expect seedborne
honeydew, inoculum, which is known to
survive for up to 7 months, to be important because
once the seed is sown, the inoculum
would not survive in the soil. In addition since
infection occurs through florets and not through
roots, seedborne inoculum would not initiate
the disease.
Andrews: What is the relative importance of ergot
compared with other disease? Is it a major
problem on perfectly fertile cultivars or is it an
induced problem with male steriles or imperfectly
fertile hybrids?
Mughogho: Ergot is important in both cases. In
Rwanda, I have seen epidemics of ergot in per-
fectly fertile varieties in farmers' fields where
landrace cultivars were grown. We may consider
it more important in hybrid seed production
because of the loss in seed for the next crop.
It is this aspect of the disease that has become
prominent in India and Thailand.
Laing: What is the origin of the quantitative,
nonspecific resistance against head smut? You
mentioned new resistant cultivars with highlevel,
race-specific resistance being deployed in
the USA. This is classical vertical resistance
(VR). Do you think this VR can be utilized without
creation of "boom and bust" cycles? Do you
think this VR can be used usefully in subsistence
agriculture?
Frederiksen: The source of the quantitative resistance
is BTS 399 (Wheatland). Tx 399 is an old
stiff-stalked inbred used for seed production.
No, and I argue against deployment of VR in
areas where smut is endemic.
King: I believe it is extremenly important to determine
yield loss associated with long smut A
panicle can look as rough, as if it is heavily infected
with long smut, even though only a low proportion
of the florets are producing sori
compared to those producing grains. I believe
long smut is a disease in which actual yield loss
can easily be over estimated.
Guiragossian: Have there been studies on
the inheritance of resistance to long smut of
sorghum?
Frederiksen: Some studies are being proposed
in Niger, Mali, and Sudan.
Hulluka: I observe long-smut occurrence when
we have drier seasons. Would that be due to
differential growth rates of the host and
pathogen?
Frederiksen: The disease occurs in very dry sorghum-growing
regions of Africa and Asia, and
frequently it is more severe in the very dry
years.
Mushonga: What is the effect of grain mold on
animal feed?
Forbes: Some studies show little or no effect on
363