Sorghum Diseases in India

20
Figure 10. Free p-coumaric acid in sorghum
glumes that were inoculated with F. moniliforme
at anthesis and evaluated during caryopsis
development. Legend: (see Fig. 7).
weathering: endosperm texture, pericarp thickness,
surface wax, and grain integrity. A more
corneous endosperm texture, e.g., grain with a
larger proportion of corneous to floury endosperm,
usually exhibit less weathering (Glueck
and Rooney 1980). Mycelia of fungal colonies do
not easily penetrate the dense, tightly packed
aleurone and peripheral endosperm layers of
mature caryopses.
A thin paricarp on sorghum caryopsis normally
corresponds to less weathering (Glueck
and Rooney 1980). Since fungal colonies were observed
inside the pericarp in all sorghum cultivars,
nutrients in the pericarp are readily hydrolyzed by
saprophytic fungi. Hence, a thick mesocarp that
contains starch and protein supports more fungal
colonies than sorghums with a thin mesocarp.
Also, most of the free phenolic compounds are located
in the pericarp and the adjoining testae layer.
These apparently bioactive compounds would be
diluted with starch, etc., in a thick pericarp.
270
10
0
20
10
0
20
10
(R)
(M)
(S)
0
0 10 20 30 40 50
Time after anthesis (days)
30
25
20
15
10
5
0
20
15
10
5
0
20
15
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(R)
(M)
(S)
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5 15 25 35 45 55
Time after anthesis (days)
Figure 11. Free p-coumaric acid in sorghum
caryopses that were inoculated with F. moniliforme
at anthesis and evaluate during caryopsis
development. Legend: (see Fig. 7).
Glueck and Rooney (1980) reported that the
surface wax of the grain is thicker and continuous,
and thus more protective, in grain of
weathering resistant cultivars. Fungi were not
able to penetrate the wax-covered, epicarp surface.
Nor could water penetrate the epicarp.
Hence, water and fungi probably enter the grain
through holes on the surface of the epicarp, i.e.,
through the hylar and stylar areas.
The rate of absorption of water by the endosperm
affects its rate of deterioration (Glueck
and Rooney 1980) (Fig. 13). Water enters the
cross and tube cells of the pericarp, and rapidly
moves around the grain. Concurrently, water
moves through the hilum (black layer) into the
germ. After 30 min, water had moved into the
area where the endosperm, germ, and pericarp
meet. Some water also enters the grain through
the style, and moves around the grain in the
cross and tube cells. Water then moves readily
through the less organized floury endosperm.