Lesson Outline
Deana Namuth-Covert
Agronomy & Horticulture Exten Assoc Professor
dcovert2@unl.edu
Breeding for Grain Quality Traits: The challenges of measuring phenotypes and identifying genotypes.
Simple inheritance of grain quality traits
When one or two genes control the variation a plant breeder observes in offspring from their crosses they have more control over their eventual success. They will be able to predict how the trait will be passed to offspring and the numbers of offspring needed to generate to insure success. In fact, they will tend to observe the grain quality phenotypes in predictable ratios. This observation is typical when dealing with qualitative traits where the seeds can be placed into discrete categories.
When Dr. Baenziger crosses a red wheat by a white wheat, he will typically get all red F1 offspring. If the F1s are allowed to self-pollinate, most of their offspring are also red but about 1 in 64 will be white. These white seeds can be planted, self-pollinate and all white offspring will be generated. Dr. Baltenspurger finds a similar situation with waxy proso millet. Most nonwaxy X waxy crosses produce non-waxy F1 offspring. F2s will consist of 15/16 non-waxy and 1/16 waxy. The waxy types are true breeding. Fig. 6 below describes why the 1/16 and 1/64 ratios are expected in these two examples. The take-home message is that when just a few genes control seed trait variation, a breeder will know what to expect and how to generate the necessary families.
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| Fig. 7. Simple genetic control of some seed traits. |
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