INTRODUCTION TO PLANT BREEDING

AGRONOMY 815 / COURSE NOTES

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

DEPARTMENT OF AGRONOMY / UNIVERSITY OF NEBRASKA

BREEDING FOR MORPHOLOGICAL AND
PHYSIOLOGICAL TRAITS

Ref. Wilson, D. 1981. p 233-290 in Frey(ed) Plant Breeding II

Evans, L.T. 1984. Physiological aspects of varietal improvement. p. 121-146 in Gustafson (ed)
Gene Manipulation in Plant Improvement. Plenum Press.

Neyra, C. D. 1985. Plant breeding: Biochemistry and crop productivity. p. 3-13 in Neyra (ed)
Biochemical basis of plant breeding. Vol. 1 Carbon metabolism. CRC Press.

All crop production ultimately depends on photosynthesis, although respiration (wish to reduce photorespiration in C3 plants), translocation and activity of metabolic sinks are all important.

Photosynthetic efficiency: Different ways of measurement:

Genetic variation exists for the components of these characteristics.

Increased biomass, however, is not always related to grain yield.

Economic yield -- Harvest Index (how biomass is partitioned) e.g., Short-strawed cereal varieties . . . lodging resistance. Note needed a completely new and different input package.

Yield usually has low heritability and so considerable interest in the effects of selecting for yield components such as . . . grain number per head, grain size, panicles per plant, etc., which may be more highly heritable. Traits however are often compensatory. These component characteristics may be considered in combination in the form of a selection index. (the use of an index will always slow progress).

Ease of measurement and heritability -- critical factors influencing whether a particular trait should be included as a selection criterion.

Identification of major constraints to yield potential/crop productivity. Team effort important. Plant Physiologist-Plant Breeder. As well as characteristics already mentioned that have received considerable attention in research studies, the following should also be considered:

All are complex traits and thus not easy to manipulate in a breeding program.

Two requirements for a successful program in breeding for physiological/morphological traits . . .

1. Simple and rapid analytical procedures with high degree of repeatability to minimize sampling and environmental problems.



2. Extensive survey of the germplasm of the species should be undertaken to identify the range of variability that exists.

(Sprague, G.F. 1969. p 375-389. In Eastin et al., (ed.) Physiological Aspects of Crop Yield. ASA.CSSA.)

Most breeders select hard within crosses in early and late generations. For complex traits (i.e., hard to measure), can use physiology to select parents, then breed for yield, etc., without measuring the physiological traits.