Self- and cross-fertility relationships and cytology of autotetraploid sweet clover, Melilotus alba
1944
Johnson, I.J. | Sass, J.E.
1. Autotetraploid plants of biennial white sweet clover, M. alba. were produced by submerging the cotyledons and the terminal bud in 0.05% colchicine solution for 6 hours. 2. Tetraploid plants had larger vegetative and floral organs, larger leaf and root cells, and larger somatic nuclei than the diploids. 3. Periclinal chimeras and islands of tetraploid tissue occurred in the roots of treated plants. Except for cell size, histological organization of leaves and roots of diploid and tetraploid plants was identical. 4. Chromosome lagging at the first meiotic metaphase ranged from complete absence of irregularity to markedly irregular distribution. The highest number of chromosomes in a telophase group was 19; the lowest, 12. Univalent, bivalent, quadrivalent, and rare trivalent associations have been observed. 5. Pollen grains of the tetraploids were significantly larger than the diploids and were also different in shape. The uniformity of pollen grain size was not different from those of the diploids. 6. Tetraploid plants varied significantly in self-fertility, indicating a possibility of selection for higher levels. 7. Significant differences were obtained in cross- and self-fertility in 4 of 32 matings. The differences could not be explained on the basis of pollen condition or on the basis of lack of normal egg cells. 8. The F1 generation plants, from crosses between parents differing in self-fertility, showed significant variability in self-fertility.
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