Sorghum Diseases in India

high levels of free phenolic compounds and tannins
occurred during the period of early invasion
and colonization of fungi of the caryopses.
Hence, it is likely that these compounds or specific
components of these compounds are involved
in the resistance mechanisms of grain
weathering.
Phenolic compounds and acids were quantified
in sorghum grown under conditions that
yielded clean and weathered grain (Waniska et
al. 1989). Higher levels of free phenolic acids,
especially p-coumaric and caffeic acids, were observed
in susceptible cultivars grown in the wet
environment (Fig. 5). Bound phenolic acids were
present at higher levels than free phenolic acids
in all cultivars; however, bound phenolic acids
did not significantly correlate with weathering
resistance. Resistant and susceptible cultivars
without a pigmented testae were properly
grouped using a statistical procedure called the
principal component analysis (Fig. 6). When
the cultivars were grouped by pericarp color,
weathering resistance, and environmental conditions,
a scatter plot of free p-coumaric acid vs.
free phenolic compounds separated the resistant
(left) and susceptible (right) groups of the scatter
plot. The higher levels of phenolic acids in
weathered, susceptible cultivars probably resulted
from fungal metabolites. Hence, analysis
of phenols in the grain can predict the level of
Figure 6. Classification of sorghum cultivars
into resistant (left) and susceptible (right)
groups according to the phenolic acid
composition.
268
50
40
30
20
10
0
0 0.3 0.6 0.9 1.2 1.5 1.8
p-coumaric acid (µg caryopsis -1 )
Red pericarp = R, White pericarp = W, Weathered environment
= *
resistance to weathering. Verification is the objective
of current projects at Texas A&M University
and ICRISAT.
A developmental study of phenols in sorghum
caryopses and glumes after inoculation
with Fusarium moniliforme revealed differences
in tissues, cultivars, and phenolic components
(Figs. 7-12) (Forbes 1986). Glumes (including
other spikelet tissues) contained relatively high
Control
400
300
200
100
0
200
150
100
50
0
200
150
100
50
SC 103-12
(resistant)
Tx 2536
(susceptibl
SC 630-11
SC 599-6
CS3541
Tx412
(R) Resistant
Inoculated
(M) Moderately resistant
(S) Susceptible
0 0 10 20 30 40 50
Time after anthesis (days)
Figure 7. Free phenolic compounds in sorghum
glumes that were inoculated with Fusarium
moniliforme at anthesis and evaluated
during caryopsis development.