Sorghum Diseases in India

Table 7. Mean threshed grain mold rating (TGMR) 1 Table 7. Mean threshed grain mold rating (TGMR) , and physical and chemical characterstics of
grain of six groups of sorghum hybrids, ICRISAT Center, rainy season 1985.
1 , and physical and chemical characterstics of
grain of six groups of sorghum hybrids, ICRISAT Center, rainy season 1985.
Testa and
Floaters (%) 3 Dehulling
spreader Pericarp Lines recovery Tannin Flavan
genotypes color (no.) Testa 2 TGMR A B (%) 4 (Cat. eq)5 4-ol
b1b1B2B2ss/ White 4 - 5.0 76 84 64 0.01 0.07
b1b1B2B2Ss
B1B1b2b2SS Red 3 - 4.6 61 74 65 0.03 1.10
B1B1b2b2Ss Red 2 - 3.5 25 27 86 0.03 3.08
B-B2-ss Brown 5 + 4.7 89 94 53 0.32 0.35
B1-B2-S- Brown 6 + 3.1 85 91 62 1.74 1.84
B1-B2-S- Brown 2 + 2.0 15 25 86 3.86 3.96
SE ±0.16 ±1.93 ±3.53 ±1.86 ±0.07 ±0.19
1. TGMR = Threshed grain mold rating on a 1 to 5 scale, where 1 = no mold, and 5 = more than 50% grain surface
area molded.
2. Testa present (+); testa absent (-).
3. Floater A - % grains in a sample that floated in a solution of NaNO3 NaNO3 NaNO3 NaNO3 NaNO3 NaNO3 NaNO3 NaNO3 (1.3 specific gravity).
Floater B = % grains in a sample that floated in a 1.327 specific gravity solution of tetrachlro-ethylene and
odorless kerosene.
4. Percentage of whole grains recovered after dehulling.
5. Cat. eq = Catechin equivalent.
hybrids with the spreader gene (B1B2-S-) were
high in tannin content and were mold-resistant,
while the hybrids with a recessive spreader gene
(B1-B2-ss) were low in tannin content and were
mold-susceptible. The grains of these hybrids,
irrespective of color of their male parents, were
low in flavan-4-ol and their grains were soft
with floury endosperm.
The mold-susceptible male parents having
testa layers and testing low in tannin content
(B1-B2-ss) produced brown-grained mold-resistant
hybrids on SPL 117 A, but brown-grained
mold-susceptible hybrids on SPL 79 A. The difference
between the two groups of hybrids lies
with the spreader gene. Hybrids on SPL 117 A
have dominant spreader gene (B1-B2-S-) and are
therefore high in tannin content, while those on
SPL 79A have the recessive spreader gene (B1-
B2-ss) and are therefore low in tannin content.
The red-grained mold-resistant male parents
(IS 14384 and IS 14390) produced brown-grained
mold-resistant hybrids on SPL 117 A and redgrained
low mold-susceptible hybrids on SPL 79
A. Hybrids on SPL 117 A were highly resistant
because they have a dominant spreader gene
(B1-B2-S-), contained high tannin levels and
moderate flavan-4-ol levels, and possessed hard
and vitreous grains. On the other hand, hybrids
on SPL 79 A were low mold-susceptible because
they did not have the testa layer and were therefore
low in tannin, but differed from the red
susceptible hybrids in that they contained moderate
levels of flavan-4-ol and their grains were
hard and vitreous. The red-grained male parents,
however, had higher levels of mold resistance,
probably because they contained significantly
higher levels of flavan-4-ol and their
grains were harder and more vitreous than those
of the progeny
Except for tannin, phenotypic correlations
among hybrids and parental lines (white- or redseeded
without testa, and brown-seeded with
testa) were significant at the P=0.01 level; (so
only in the brown-seeded lines) indicating that
high tannin level (testa with spreader gene),
high flavan-4-ol, and grain hardness influence
mold resistance, independently or in combination.
White-grained sorghums do not contain
tannin and so far none has been found to contain
appreciable amounts of flavan-4-ol Mold resistance
in white-grained sorghum lines probably
is due to grain hardness or unidentified polyphenolic
compounds. Hahn et al. (1984) reported
both a greater variety and amount of
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