Sorghum Diseases in India

hardness and its relationship to digestibility and
mold resistance deserve high priority.
Effect of Testa Layer and Spreader
Genes
Sorghum lines high in tannin content and having
the testa layer were reported to be more resistant
to grain mold fungi by Glueck and Rooney
(1980). The presence or absence of the testa layer
is controlled by the B1 and B2 genes. The testa
layer is present when the B1 and B2 genes are
both dominant (B1-B2). A dominant spreader
"S" gene in the presence of a testa layer results
in brown-grained with high tannin. We investigated
the effect of various combinations of the
testa layer and spreader genes on mold resistance
in 2 female and 11 male lines and their
hybrids.
280
60
50
40
30
20
10
0
Floaters (%):
1 = 0 to 10% floaters
2 = 10 to 20% floaters
3 = 20 to 30% floaters
4 = 30 to 40% floaters
5 = 40 to 50% floaters
6 = 50 to 60% floaters
7 = 60 to 70% floaters
8 = 70 to 80% floaters
9 = 80 to 90% floaters
10 = 90 to 100% floaters
White-grained
Red-grained
Brown-grained
1 2 3 4 5 6 7 8 9 10
Floaters (%)
Figure 5. Frequency distribution of floaters (%) among white, red, and brown-grain F2 segregates
derived from a cross between IS 14384 (red-grained) and SPV 104 (white-grained) sorghums.
We crossed the 11 male lines with SPL 117 A
and SPL 79 A male-steriles with b1b1B2B2SS and
B1B1b2b2ss testa and spreader genotypes respectively
(Bhola Nath et al. 1985) and produced
22 hybrids with various combinations of testa
and spreader genotype. The male lines were
grouped into white- and red-grained moldsusceptible;
red-grained mold-resistant; and
brown-grained mold-susceptible. These hybrids,
together with their female and male parents,
were evaluated for mold resistance in a
randomized-block design with three replications
during rainy season 1985 at ICRISAT Center. The
testa and spreader genotypes, grain color, and
mold resistance ratings of the 2 females, 11
males, and their hybrids are presented in Table
5.
Grains of the hybrids and parental lines were
scored for mold resistance 54 days after 50%
flowering and the floaters (%), dehulling recov-