Some effects of inbreeding in sugar beets

In 1925, 300 well-shaped sugar beets were selected from a commercial field of the Janascz variety. Sugar tests, later examination of root shape, and a few storage losses reduced this number to 120, of which 100 grew. A few branches of 75 of these mother beets were covered just before the flowers opened with 2-pound grocery bags and seeds were obtained under bags from 59 of the plants. Seeds from the uncovered branches of the same plants were harvested and designated as open-pollinated, whereas the seeds grown under bags were designated as selfed. Selfed seeds from 20 of the 59 strains were sown during the fall of 1926 in the greenhouse and thinned to 10 beets in a 6-foot row. Ordinary electric light was applied from dark till 10 o'clock in the evening. In the spring five beets from each row were harvested a month early and stored in a good potato cellar. The other five were removed a month later directly to the field and planted in the same row with the ones from the cellar. All beets from seeds sown in October or November set seeds in the field in August. No difference due to storage was observed. A similar treatment was given the next fall and winter with the same result, except some strains sown in January in the greenhouse produced little seed. During the third fall and winter, due to lighting difficulties, light was applied only for an hour or so except during the last 3 weeks before the beets were transplanted to the field when it was applied from dark till 9 or 10 o'clock. When set in the field these beets seeded poorly. Each year the greenhouse grew cool at night, that is, the temperature dropped to about 50 degrees or 55 degrees F. In the daytime, being a horticultural house, it was kept exceptionally warm (70 degrees to 80 degrees F). Each season a few strains of beets were grown in the greenhouse during the winter, thus going from seed to seed each year. Practically every strain treated this way was selfed in consecutive generations. Any selfed seeds that were not grown in the greenhouse were seeded in the field the following spring along with open-pollinated strains. All the open strains studied had greenhouse ancestry, that is, they had been selfed one, two, or more generations. Seeds from such selfed lines were harvested both from under grocery bags and from uncovered branches. Only small quantities of selfed seeds were available, but enough was always obtained to keep the lines going. The selfed seeds of some strains germinated poorly, but the seeds of other strains did almost, if not fully, as well as open seed. Meanwhile, a much larger population of seed plants was grown from roots stored over winter. These were divided into two somewhat equal groups, one for seed and one for roots each year. Nearly all strains occurred in each group. In 1920, a large enough quantity of seeds for a field test was obtained from strains that had been selfed two or three generations but exposed to open pollination in 1928, that is, F1 seed. Some of these strains in the field rows appeared to be highly uniform. Measurements taken on leaf length and width and on petiole length and width and compared to similar data from the commercial parent variety showed, as measured by coefficients of variability, an appreciable number of strains to be more uniform in these four plant characters than was the parent variety. The Utah strains compared favorably in degree of uniformity with 200 strains selfed by W.W. Tracy by means of individual plant isolation. Several strains from one original plant were practically uniform for a strongly crinkled leaf in the vegetative year and for extremely leafy seed stalks in the seed year and for uniformly small-sized seeds. There was a distinct segregation in the group of strains for size of seed. Some abnormalities were found. One strain was almost pure for a leaf blotch not recognized by a well-trained plant pathologist as being any known disease. Chlorophyll was reduced and the condition seemed hered