Material Detail

Monogerm sugar-beet varieties have not been developed in either Europe or America. Failure to develop such varieties is due to difficulties in de- tecting monogerm plants. Monogerm mutations are correlated with late- bolting ability and are ordinarily eliminated by natural selection. It is necessary to examine an enormous number of plants in different varieties to find monogerm races.

In 1948 an expedition to search for monogerm sugar beets was organized by the U. S. Department of Agriculture and the Curly Top Resistance Breed- ing committee with the assistance of the West Coast Beet Seed Company. In accordance with Dr. F. V. Owen's advice the plan involved two trips. I made the first trip in June to California and Oregon with Dr. Eubanks Carsner, Dr. J. S. McFarlane, Dr. R. A. Pendleton, Dr. H. Savitsky and Mr. Sam C. Campbell to choose seed-beet plantings with a wide choice of varieties and with the best opportunity for selection work. I made a second trip in July to Oregon for an intensive search for monogerm beets in selected fields just prior to the harvest period. I succeeded in finding five monogerm sugar-beet plants in the variety Michigan Hybrid-18 in a four-acre field with approximately 300,000 plants. This variety was the only variety in which I found true monogerm seed beets. I made a similar intensive search in Utah with Messrs. Myron Stout, C. H. Smith, Vernal Jensen and Dr. H. Savitsky in curly-top-resistant varieties, but it was unsuccessful. Plants having bilocular seed balls for the most part were found in all these varieties.

All five of the monogerm plants were late in floral development. More than half of their fruits were not ripe at the time of harvest. The selected plants were observed to be self-fertile during two generations. Approximately 75 percent of their progeny arose from selfing under open pollination. The selfed progenies consisted of very uniform monogerm plants which manifested considerable variation in time of bolting and flowering. F1 hybrids between mono- and multigerm sugar beets were significantly more early bolting than the homozygous monogerm plants and produced variable F2 progenies. F1 progenies after selfing showed much greater variation in all characters than the progenies of selfed monogerm lines. Two of the five selections (races S.L.C. Monogerm 101 and 107) were very similar and it is evident that they originated from lines which had selfed for several generations. The other three selected races differed in characters of fruits, rosettes and seed beets.