INTRODUCTION TO PLANT BREEDING

AGRONOMY 815 / COURSE NOTES

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

DEPARTMENT OF AGRONOMY / UNIVERSITY OF NEBRASKA

QUALITY IMPROVEMENT

		Nutritional value	e.g., protein quality in cereals digestibility in forages, etc.
Quality		Commerical utilization	e.g.,baking quality oil content brewing quality fiber characteristics
		Consumer appeal . . . . .	vegetables, fruits

Ref. Axtell, J.D. 1981. Breeding for improved nutritional quality, p 365-432. In Frey (ed.) Plant Breeding II. Iowa State University.

TEAM EFFORT

Nutritionists need to provide clear-cut nutritional objectives to the breeder (these objectives are often either unknown or changing). Plant breeders need to provide information of what variation exists and thus what potential for improvement should be possible in addition to what tradeoffs may be involved. e.g., Increased protein quality sometimes lower grain yield. This was the case with the opaque-2 (o2) was introduced into corn. In a comparison of a normal maize hybrid and its o2 counterpart over a 4 year test, Glover (1976) found a 10% reduction in yield attributable to o2. However, yield can be maintained while improving protein -- Lancota has a 1-2% protein increase without a yield decrease.

Breeding for nutritional traits

Important considerations in breeding for quality characteristics:

1. Quality characteristics are generally very complex.
   
   
2. Lab facilities with a chemist and skilled lab technicians are often required to do testing. (There are regional quality testing laboratories located in major production areas of the U.S.)
   
   
3. The testing stage for new varieties developed in a breeding program is often not until they have reached the advanced field test stage since fairly large quantities of seed/fiber are often needed for quality evaluation. Assays are often destructive; therefore, it can be difficult to work with segregating materials -- are not testing what you are growing. A key question facing breeders is when to look at quality traits: it is a trade off of how important is the quality trait and how expensive and time consuming is it to screen for the trait. Can lines be eliminated before the quality tests need to be done.
   
   

   However, simple quality testing procedures are needed by breeders for early screening.

   Requirements . . . Inexpensive.

   Must be able to screen large numbers of experimental strains/families/individual plants before yield testing (generally the most expensive part of a breeding program). Preliminary quality screening does not need to be too exact, provided the individuals with greatest potential are accurately identified. Fine tuning can be done later when agronomically superior individuals have been selected and sufficient seed/fiber available. Ranking is often good enough.

ANOTHER KEY DIFFICULTY THAT BREEDERS FACE WITH QUALITY IS THAT THERE IS RARELY AN ECONOMIC INCENTIVE FOR IMPROVING QUALITY. QUALITY IS EMPHASIZED IN TIMES OF SURPLUSES, QUANTITY IN TIMES OF SHORTAGES.. In 1989, high protein wheat was in surplus, for the first time in many years, spring wheat was sold at a disadvantage to winter wheat at equivalent protein content.

See Axtell for examples of breeding for nutritional quality.