Sorghum Diseases in India

Cereal Chemistry and Grain Mold Resistance
R.D. Waniska 1 , GA Forbes 2 , R. Bandyopadhyay 3 ,
R.A. Frederiksen 4 , and L.W. Rooney 5
Abstract
Grain of sorghum at immature and mature stages of development is deteriorated by fungi Sorghum
cultivars that exhibit some resistance to deterioration have a more corneous endosperm,
contain specific phenolic compounds, are thin in pericarp thickness, and show decreased fissuring
or cracking in the field. Resistant cultivars respond more quickly than susceptible cultivars to
fungal invasion via increased levels of phenolic compounds in glume tissues. Extensive deterioration
of the grain does not occur before physiological maturity because the developing grain
contains 3 to 10 times the level of specific phenolic compounds of mature grain. In sorghum grown
under wet conditions, grain of resistant cultivars contains lower levels of free phenolic compounds
at maturity compared with grain of susceptible cultivars. Hence, phenolic compound content in
gram is a predictor of the sorghum cultivar's level of resistance to grain molding.
Introduction
Grain of Sorghum bicolor (L.) Moench is exposed
to sunshine, rain, diseases, and pests during its
development. Grain molding or weathering refers
to deterioration of the grain by several
mechanisms (Glueck and Rooney 1980; Williams
and Rao 1981), i.e., chemical, enzymatic, bacterial,
fungal, and due to insects. Regardless of the
cause, changes in the physical properties of
grain include (1) moldy and discolored pericarp,
(2) a soft and chalky endosperm, (3) decreased
grain filling and size, (4) sprouting (reduced germination
of seed), (5) mycotoxins, (6) decreased
dry matter, density and test weight, and (7) altered
composition of phenolic compounds (Glueck
and Rooney 1980; Williams and Rao 1981;
Jambunathan et al. 1986.
The changes that occur in the seed when sorghum
deteriorates in the field as a result of at­
tack by molds are reviewed. The terms 'molding'
and 'weathering' will herein be used interchangeably.
Invasion by Fungi
Fungi are responsible for much of the damage
during early and later stages of deterioration
(Glueck and Rooney 1980; Williams and Rao
1981). Bacteria and fungi invade and colonize
spikelet tissues at anthesis (Fig. 1) (Castor and
Frederiksen 1980). After the glumes open at anthesis,
reabsorption of the lodicules and related
tissues by the plant commences (Castor and Frederiksen
1980). Many saprophytes, including
species of Curvularia, Fusarium, and Colletotrichum,
also utilize these tissues as nutrients
(Castor and Frederiksen 1980; Glueck and
Rooney 1980). These fungi colonize glume tis-
1. Associate Professor, Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843-2474, USA.
2. Plant Pathologist, Centre Internacional de la Papa, International Potato Center, PO Box 5969, Lima, Peru.
3. Plant Pathologist, Cereals Program, ICRISAT Center, Patancheru, Andhra Pradesh 502 324, India.
4. Professor of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2474, USA.
5. Professor, Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843-2474, USA.
Waniska, R.D., Forbes, G.A., Bandyopadhyay, R., Frederiksen, R.A., and Rooney, L.W. 1992. Cereal chemistry and grain mold
resistance. Pages 265-272 in Sorghum and millets diseases: a second world review. (de Milliano, W.A.J., Frederiksen, R.A., and
Bengston, G.D., eds). Patancheru, A.P. 502 324, India-International Crops Research Institute for the Semi-Arid Tropics. (CP 735)
265