Sorghum Diseases in India

say, sooty stripe and leaf blight. You mentioned
that both sooty stripe and leaf blight are important,
because they affect large areas of the leaf.
Chintu: Oval leaf spot, compared with sooty
stripe and leaf blight, is less important because it
occurs after the crop is mature.
King: Is the covered smut you mentioned
caused by Tolyposporium penicillariae? Did you
say that you can control it by a seed treatment?
This would be very unusual.
Muza: Johnson, D.T. (1968) seems to indicate so.
I refer to his "Bulrush millet (Pennisetum typhoides)~--Aa\
important traditional grain.'' Bulletin
2509, Zimbabwe Agricultural Journal, Pages
1.9-23.
Thomas: In one of your tables you showed some
lines that were resistant at Kamboinse but susceptible
at Fada. Kamboinse and Fada are only
260 km apart. How do you explain this?
Paco: It is probably due to the difference in isolates
in the two locations. We have also some
lines which are resistant at Fada and susceptible
at Kamboinse.
Andrews: In your last table, how much yield
loss does 43% incidence mean?
Paco: Yield loss was not measured in this trialbut
in another trial on farmers' fields, metalaxyl
treatment increased yields by 20%.
Mtisi: Would you please explain what was used
in treatment 5?
Paco: Metalaxyl is the active ingredient of Apron
35®.
Adipala: Have you examined Xanthomonas campestris
isolates from finger millet? We have issued
isolates from Uganda deposited with CMI
which we think are members of X. campestris
group.
Qhobela: No, we have not
King: What is the significance of sowing the tall
photoperiod sensitivity African variety every 25
rows in your anthracnose nursery?
360
Duncan: To reduce wind movement and hold
morning dews on the plants for a long period. In
effect, it creates a field-based incubation chamber
where natural build-up and spread of Colletotrichum
graminicola occurs, and it helps
reduce replication x replication variation among
the trials.
de Milliano: Do you think it is really better to
use four pathotypes of C. graminicola instead of
one? Possibly, you may be increasing the genetic
variability by increasing the number of
pathotypes.
Duncan: Yes, it is a possibility. I could be creating
more pathotypes by the screening techniques
that I use. But I have learned to readjust
my breeding techniques to the point that I have
a better probability now of having resistance in
this breeding material if a new pathotype
emerges. I need the four differentials (susceptibles)
in my nursery to monitor development of
the disease on a year by year basis for evaluation
purposes.
Mohamed Ali: You mentioned that johnsongrass
can serve as a reservoir host for the
sorghum isolates of C graminicola. In our crossinoculation
studies, different sorghum isolates
with varying levels of virulence did not infect
johnsongrass.
Duncan: All our isolates originate from johnsongrass.
That is the rule for us instead of the
exception. Perhaps the one strain of johnsongrass
that you used was resistant. Try two or
three different strains from around the area.
Johnsongrass is quite variable itself.
Frederiksen: Dr. Duncan, we have noted your
populations of C. graminicola vary from year to
year.
Duncan: I have quite a unique pathogen population
situation which varies according to environmental
(moisture, heat) conditions. The research
that Dr. Cardwell has conducted will hopefully
shed some light on the dynamics of this pathogen
population.
Mughogho: I would like to make a correction in
the presentation. Anthracnose was not first described
in Texas in 1911; but in Togo in 1902 and