Sorghum Diseases in India

mid-1970s. Murty et al. (1980) reviewed the progress
and achievements of ICRISAT's GMbreeding
research. ICRISAT scientists crossed a
large number of low mold-susceptible, whitegrained
sources and adapted high-yielding
lines, then intensively screened and selected for
mold resistance in early-segregating populations.
They identified lines with moderately
high grain-yield potentials and resistance to
grain molds under low disease pressure. However,
under moderate to high mold disease pressure,
these lines became susceptible. We still do
not have improved white-grained cultivars that
farmers can use without a potential for GM loss.
I believe that the lack of progress can be attributed
to the low levels of resistance in the material
available for use in breeding programs. Various
sources of low susceptibility were intermated to
generate variability and concentrate the scattered
resistance genes, but this did not significantly increase
the levels of GM resistance.
The identification, in 1981, of high levels of
mold resistance in colored-grain sorghums without
the tannin-containing testa layer was a significant
achievement, as it indicates that mold
resistance in colored-grain sorghums isn't always
associated (as previously believed) with
high tannin levels. Thus, it may be possible to
transfer their genes for moid resistance to whitegrained
sorghums. In 1982, we started using
mold resistant, colored-grain sorghums to investigate
the possible transfer of the high levels of
resistance in colored-grain to white-grained sorghums
through breeding.
Screening and Selection
We made crosses between mold-resistant, colored-grain
sorghums (IS 14384, IS 14385, and
IS 14388) and mold-susceptible, white-grained,
high-yielding cultivars (ICSV 1 and SPV 104).
IS 14384 does not have the tannin-containing
testa layers, but IS 14385 and IS 14388 do.
Using the GM field-screening techniques developed
at ICRISAT (Bandyopadhyay and
Mughogho 1988), we screened F1 and F2 segregating
progenies for resistance. Five hundred or
more plants were screened from each cross and
for each individual plant, time to 50% flowering
was recorded. Harvesting of each panicle was
carried out 54 days after flowering (i.e., 2 to 3
weeks after reaching physiological maturity),
threshed grains of each panicle were rated for
GM resistance on the 1 to 5 scale. Recording the
time to 50% flowering for each individual plant
is tedious and time consuming, but essential to
ensure that developing grains of each plant were
exposed to wet and humid environmental conditions
(ideal for mold development) for an
equal number of days. This avoids mistaking
late-maturing genotypes as GM resistant, and
improves the probability of identifying mold resistance
in early-maturing genotypes.
Table 1. Frequency of mold-resistant, white-grained genotypes in F2 segregating populations derived
from crosses between mold-resistant, colored-grain sorghums, and mold-susceptible, whitegrained
sorghums at ICRISAT Center, rainy season 1983.
Total F2
Total white-grained
progenies
in F2 Population
Selected white-grained
F2 progeny
Pedigree populations (no.) (%) (no.) (%)
IS 143841 x KSV 1
IS 143841 x SPV 104
KSV1 x IS 14385 1
SPV 104 x IS 14385 1
IS 14388 1 x KSV1
IS 14388 1 x SPV 104
550
340
554
561
627
521
1. Mold-resistant, colored-grain sorghum parent.
48
59
152
68
77
63
9
17
27
12
12
12
12
12
18
15
2
1
2.0
3.5
3.2
2.7
0.3
0.2
275