Sorghum Diseases in India
Sorghum Diseases in India
Sorghum Diseases in India
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mid-1970s. Murty et al. (1980) reviewed the progress<br />
and achievements of ICRISAT's GMbreed<strong>in</strong>g<br />
research. ICRISAT scientists crossed a<br />
large number of low mold-susceptible, whitegra<strong>in</strong>ed<br />
sources and adapted high-yield<strong>in</strong>g<br />
l<strong>in</strong>es, then <strong>in</strong>tensively screened and selected for<br />
mold resistance <strong>in</strong> early-segregat<strong>in</strong>g populations.<br />
They identified l<strong>in</strong>es with moderately<br />
high gra<strong>in</strong>-yield potentials and resistance to<br />
gra<strong>in</strong> molds under low disease pressure. However,<br />
under moderate to high mold disease pressure,<br />
these l<strong>in</strong>es became susceptible. We still do<br />
not have improved white-gra<strong>in</strong>ed cultivars that<br />
farmers can use without a potential for GM loss.<br />
I believe that the lack of progress can be attributed<br />
to the low levels of resistance <strong>in</strong> the material<br />
available for use <strong>in</strong> breed<strong>in</strong>g programs. Various<br />
sources of low susceptibility were <strong>in</strong>termated to<br />
generate variability and concentrate the scattered<br />
resistance genes, but this did not significantly <strong>in</strong>crease<br />
the levels of GM resistance.<br />
The identification, <strong>in</strong> 1981, of high levels of<br />
mold resistance <strong>in</strong> colored-gra<strong>in</strong> sorghums without<br />
the tann<strong>in</strong>-conta<strong>in</strong><strong>in</strong>g testa layer was a significant<br />
achievement, as it <strong>in</strong>dicates that mold<br />
resistance <strong>in</strong> colored-gra<strong>in</strong> sorghums isn't always<br />
associated (as previously believed) with<br />
high tann<strong>in</strong> levels. Thus, it may be possible to<br />
transfer their genes for moid resistance to whitegra<strong>in</strong>ed<br />
sorghums. In 1982, we started us<strong>in</strong>g<br />
mold resistant, colored-gra<strong>in</strong> sorghums to <strong>in</strong>vestigate<br />
the possible transfer of the high levels of<br />
resistance <strong>in</strong> colored-gra<strong>in</strong> to white-gra<strong>in</strong>ed sorghums<br />
through breed<strong>in</strong>g.<br />
Screen<strong>in</strong>g and Selection<br />
We made crosses between mold-resistant, colored-gra<strong>in</strong><br />
sorghums (IS 14384, IS 14385, and<br />
IS 14388) and mold-susceptible, white-gra<strong>in</strong>ed,<br />
high-yield<strong>in</strong>g cultivars (ICSV 1 and SPV 104).<br />
IS 14384 does not have the tann<strong>in</strong>-conta<strong>in</strong><strong>in</strong>g<br />
testa layers, but IS 14385 and IS 14388 do.<br />
Us<strong>in</strong>g the GM field-screen<strong>in</strong>g techniques developed<br />
at ICRISAT (Bandyopadhyay and<br />
Mughogho 1988), we screened F1 and F2 segregat<strong>in</strong>g<br />
progenies for resistance. Five hundred or<br />
more plants were screened from each cross and<br />
for each <strong>in</strong>dividual plant, time to 50% flower<strong>in</strong>g<br />
was recorded. Harvest<strong>in</strong>g of each panicle was<br />
carried out 54 days after flower<strong>in</strong>g (i.e., 2 to 3<br />
weeks after reach<strong>in</strong>g physiological maturity),<br />
threshed gra<strong>in</strong>s of each panicle were rated for<br />
GM resistance on the 1 to 5 scale. Record<strong>in</strong>g the<br />
time to 50% flower<strong>in</strong>g for each <strong>in</strong>dividual plant<br />
is tedious and time consum<strong>in</strong>g, but essential to<br />
ensure that develop<strong>in</strong>g gra<strong>in</strong>s of each plant were<br />
exposed to wet and humid environmental conditions<br />
(ideal for mold development) for an<br />
equal number of days. This avoids mistak<strong>in</strong>g<br />
late-matur<strong>in</strong>g genotypes as GM resistant, and<br />
improves the probability of identify<strong>in</strong>g mold resistance<br />
<strong>in</strong> early-matur<strong>in</strong>g genotypes.<br />
Table 1. Frequency of mold-resistant, white-gra<strong>in</strong>ed genotypes <strong>in</strong> F2 segregat<strong>in</strong>g populations derived<br />
from crosses between mold-resistant, colored-gra<strong>in</strong> sorghums, and mold-susceptible, whitegra<strong>in</strong>ed<br />
sorghums at ICRISAT Center, ra<strong>in</strong>y season 1983.<br />
Total F2<br />
Total white-gra<strong>in</strong>ed<br />
progenies<br />
<strong>in</strong> F2 Population<br />
Selected white-gra<strong>in</strong>ed<br />
F2 progeny<br />
Pedigree populations (no.) (%) (no.) (%)<br />
IS 143841 x KSV 1<br />
IS 143841 x SPV 104<br />
KSV1 x IS 14385 1<br />
SPV 104 x IS 14385 1<br />
IS 14388 1 x KSV1<br />
IS 14388 1 x SPV 104<br />
550<br />
340<br />
554<br />
561<br />
627<br />
521<br />
1. Mold-resistant, colored-gra<strong>in</strong> sorghum parent.<br />
48<br />
59<br />
152<br />
68<br />
77<br />
63<br />
9<br />
17<br />
27<br />
12<br />
12<br />
12<br />
12<br />
12<br />
18<br />
15<br />
2<br />
1<br />
2.0<br />
3.5<br />
3.2<br />
2.7<br />
0.3<br />
0.2<br />
275