Sorghum Diseases in India

Vidyabhushanam: What are the disease-resistant
factors identified in A2 cytoplasm mentioned
in your presentation?
Narro: We have just started using A2 cytoplasm
as well as Al cytoplasm for hybrid production.
We have no information, at this stage, about disease
resistance using A2 cytoplasm.
Rosenow: With regard to the question by
Vidyabhushanam on what specific disease resistance
does Narro obtain from A2 cytoplasm in
Mexico, and how is A2 related to Al.
To my knowledge, there are no specific resistances
to diseases that are directly related to the
A2 cytoplasm, but are merely related to the
germplasm which we have been able to sterilize
in A2. The A2 is considerably different from Al,
and much different in fertility restoration from
Al.
Laing: How much of a problem are mycotoxins
in sorghum?
Frederiksen: Not enpugh work has been done,
but we do know that the sorghum grains are
colonized by many fungi which compete with
the mycotoxin-producing fungi. The situation
with regards to Phoma sp in Nigeria is not clear.
Teyssandier points out that T2 toxins are produced
by Fusarium spp; these toxins can be dangerous
in feeds for swine and chicks.
McGee: Following up on Frederiksen's response
as to why aflatoxin is not a problem in
sorghum:
Aflatoxin is a severe problem in maize, peanuts,
and cotton. All can be extensively invaded
by field fungi. It seems to me that the answer to
this question is more complex, because physiological
and ecological factors are involved.
Zummo: Part of the reason that aflatoxin is not a
problem in sorghum is because aflatoxin is a byproduct
of the substrate that the fungus grows
on. Sorghum is apparently not as good a substrate
for aflatoxin production as maize, cotton
seed, and groundnuts.
Frederiksen: Mycotoxins have not generally
been a serious problem in sorghum. We do not
understand why.
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Theuri: With reference to the use of tolerant
varieties for control of MDM, is it not risky to
use these varieties since there is a buildup of
virus in the tolerant variety? Why are resistant
varieties not used?
Frederiksen: Tolerance permits the survival of
the host and pathogen without producing a
screening tool for the selection of another virus
strain that may damage the host.
Mbaye: You have shown one table in which you
put (-) behind foliar diseases in France. Does it
mean that there is no foliar disease in France?
Forbes: No. The (-) means that I can present no
evidence for foliar diseases, either as a current or
potential problem. I am suggesting that foliar
diseases pose no potential threat because environmental
conditions are not conducive to foliar
diseases. This situation is similar to that found in
the northern sorghum-growing regions in USA.
Mughogho: Maize is affected by downy mildew
in Somalia. Do you know if downy mildew
also occurs on sorghum, or if the downy mildew
on maize also infects sorghum?
Hassan: Downy mildew occurs on sorghum,
but we do not know if it is the same as the one
infecting maize in the irrigated areas of Somalia.
Anahosur: You mentioned head smut control
with a fungicide. What method of treatment and
fungicide have you used?
Hassan: I was referring to covered kernel smut,
and the chemical is Fernasan D ® .
Anahosur: Are there any fungicides that can be
used to control head smut on sorghum?
Njuguna: There is experimental evidence to
suggest that Bayleton ® , manufactured by Bayer,
is effective when used as a seed dressing for
head smut of maize.
McGee: Carboxin ® controls head smut in
maize.
Theuri (to King): You illustrated the concept of
"Recovery Resistance" with downy mildew, a
disease which requires moisture for its develop-