Principles of Plant Genetics and Breeding

when the production area is isolated from other areas
where this system is not operational. Some failures of
system have occurred in leaf rust fungus in Mexico.
(a) Rusts. Diseases of importance in wheat production
include stem rust (caused by Puccinia
graminis Pers.), leaf rust (P. recondite Rob.), and
stripe rust (P. striformis West). Stem rust is
particularly devastating to wheat production.
Researchers have identified numerous physiological
races of rust species. Over 30 resistance genes
have been discovered for P. graminis and P.
recondite, and more than 16 genes for P. striformis.
(b) Smuts. Wheat is attacked by a variety of smut
diseases, the major ones being loose smut
(caused by Ustilago tritici), common bunt
(Tilletia tritici), and dwarf bunt (T. controversa).
Yield can be drastically reduced by smut. Loose
smut can destroy the entire spike, whereas other
smuts cause the grain to be replaced with smut
spores. Genes of resistance have been identified
for loose and common smut diseases.
(c) Powdery mildew. Genes encoding resistance to
powdery mildew (caused by Erysiphe graminis)
have been identified.
Acquaah, G. 2005. Principles of crop production: Theory,
techniques, and technology. Prentice Hall, Upper Saddle
River, NJ.
Hall, M.D., and D.A. van Sanford. 2003. Diallel analysis of
Fusarium head blight resistance in soft red winter wheat.
Crop Sci. 43:1663–1670.
Part A
Please answer the following questions true or false:
1 Wheat is predominantly a self-pollinated species.
2 Wheat has spikelet inflorescences.
3 Cultivated wheat is a tetraploid.
4 Gluten is a complex starch found in wheat.
Part B
Please answer the following questions:
1 What is vernalization?
2 Give the two groups of wheat on the basis of adaptation.
BREEDING WHEAT 483
References and suggested reading
Outcomes assessment
(d) Other diseases of interest in wheat breeding
include viral infections, blights, and rots.
6 Insect resistance:
(a) Hessian fly. The Hessian fly (Mayetiola destructor)
is known to cause a wide range of effects
to wheat plants including dwarfing of plants,
reduced tillering, straw breakage, and increased
susceptibility to winter injury. Some genotypes
have tolerance to the pest, being able to compensate
for reduce tillering by producing additional
tillers. Several biotypes of the fly have been
identified. Resistance genes have been identified.
Sources of resistance include genotypes such as
“Ribeiro”, “Marquillo”, and “Kawvale”.
(b) Greenbug. About eight biotypes of the greenbug
(Schizaphis graminum) have been identified.
Genes for many of these biotypes have been
identified.
7 End-use quality. Wheat is used in bakery products
and semolina. Various breeding programs focus on
various market types. The hard wheats are used for
bread, whereas the soft wheats are used for confectionary
products and cookies. Durum wheats are
used for pasta products.
Rajaram, S., A. Mujeeb-Kazi, and R.P. Singh. 1997. Wheat.
In: Genetics, cytogenetics, and breeding of crop plants. Vol. 2.
Cereal and commercial crops (Bhal, P.N., P.M. Salimath,
and A.K. Mandal, eds). Science Publishers, Inc., Enfield,
NH.