Optimal Population Density and Random vs. Selective Elimination of Genotypes Under a Modified Single-Seed Descent Method with Spring Oats1
- G. Cisar,
- A. E. Howey and
- C. M. Brown2
A modified single-seed descent (SSD) method of generation advance is used in the Univ. of Illinois spring oat (Avena Saliva L.) breeding program. The method couples high plant density with limited soil fertility and moisture levels to produce a population with a high proportion of single or few seeded plants, along with some barren plants. Questions regarding the technique are twofold: 1) what population density will yield a high proportion of plants with one or very few seeds and a minimum of barren plants, and 2) are the genotypes which are lost due to barrenness randomly or selectively eliminated?
In a series of population densities, ranging from 10 to 150 seeds per 15-cm clay pot in 10 seed increments, 30 to 40% of the plants grown at densities of 100 to 150 seedlings per pot produced single seeds. Populations of 120 to 150 seedlings per pot allows adaptation of the technique to the SSD principle with a considerable savings in harvest time and greenhouse space.
To determine whether barren plants were randomly or selectively eliminated, progenies of two segregating crosses were grown at high (60 seedlings per pot) and low (10 seedlings per pot) population densities. After two generations of modified SSD, 34.5% of the original population was lost due to barrenness at the high density in one cross and 26.5% in the other. Seed of surviving genotypes was increased for a replicated field trial where maturity (days after 1 June), plant height (cm), oil content (nuclear magnetic resonancevalue), and grain yield (g/hill plot) were measured. Means and variances between progenies advanced under high or low densities generally did not differ for any of the traits, leading to the conclusion that the genotypes eliminated due to barren plants were randomly and not selectively eliminated due to selection pressures of the technique.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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