INTRODUCTION TO PLANT BREEDING

AGRONOMY 815 / COURSE NOTES

P. STEPHEN BAENZIGER, 338 Keim Hall, 472-1538

DEPARTMENT OF AGRONOMY / UNIVERSITY OF NEBRASKA

MASS SELECTION

Fehr 24.

Plants chosen on the basis of their phenotype and harvested seed of these selections composited without progeny testing to form a mass selection, which = a mixture of a number of pure lines in self pollinated crops. This is the oldest method of crop improvement practiced by man or woman.

Method:	1. Need a large initial population (500-3,000 plants).
	2. Undesirable types are eliminated. Culling, not advancing.
	3. Usually a large number of lines are saved (e.g., 75%). i.e., Low selection intensity.
	4. The process can be repeated in subsequent generations.
	5. May be used to preserve the characteristics of a pure variety. Most common use today. ex., Siouxland 89.
Advantages:	1. 'Safe.' The genetic variation within a mass selection may provide buffering in varying environmental conditions -- i.e., broadly adapted.
Advantages:	2. Can lead to a rapid release of a variety. No progeny evaluation phase.
Disadvantages:	1. One does not know whether the plants being selected are homozygous or heterozygous (a low level of outcrossing occurs naturally in most self-pollinated species). Since heterozygous plants will segregate in the following generation, further selection may be needed in subsequent generations.
Disadvantages:	2. Genotype x Environment interaction. The environment in which a plant grows affects its development and appearance. With mass selection it is not possible to know whether the selected phenotype is superior in appearance due to heredity or to environment because mass selection is confounded with the selection environment. It does not work well for traits of low heritability or in environments were the trait is not expressed.