The breeding behavior of side-oats grama in partially isolated populations
1950
Harlan, J.R.
1. From highly variable material consisting of bulk lots from a variety of points in Oklahoma and Texas, selections for specific agronomic types were made and placed in isolation blocks. Seed harvested from each block was used to establish sample populations in which reselections for type were made. Second generation progenies were established from seed produced by the reselections under isolation. Fourteen matched plants of each type were isolated in the first generation, 12 in the second generation. 2. Eighteen types were used, including a series of growth forms, late flowering, broad leaves, narrow leaves, heavy stems, fine stems, abundant leaf production, abundant culm production, and rapid basal spread. 3. The isolation blocks were 25 feet square and 28 feet apart in each direction. The intervals were planted to a thick stand of sorghum. Genetic isolation was quite satisfactory for this type of breeding system, but was probably not complete in so short a distance. 4. Considerable progress toward fixation of some of the types was evident in a single generation. Some types bred reasonably true to type after two generations; other types were less readily fixed. 5. Characters easily fixed in a population are broad leaves, narrow leaves, fine stems, heavy stems, and late flowering. 6. Types involving abundant leaf production showed the least progress toward fixation. 7. Certain characters appeared to be closely associated in the sample populations, e.g., broad leaf and late flowering, fine leaf and rust resistance, broad leaf and blue-green color, narrow leaf and yellow-green color.
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