Genetic Stability of Haploid, Diploid, and Tetraploid Genotypes in the Tomato.

HE spontaneous origin in 1926 of a tomato haploid in Lycopersicon Tescu len lun Mill. (LINDSTROM 1929) provided the source material of these investigations. This haploid when doubled asexually by the decapitation-callus method becomes an absolutely homozygous diploid ; and doubling this in turn results in the homozygous tetraploid. Selection experiments have been in progress since 1926 in the haploid, since 1929 in the diploid, and since 1930 in the tetraploid. Cytological descriptions of these tomato forms appear in earlier reports (HUMPHREY 1934, 1937; LINDSTROM and Koos 1931; LINDSTROM and HUMPHREY 1933). The main objective of the selection experiments was to test the relative stability of the tomato genotype in the n, 2n, and 4n condition of comparable material. An original haploid plant may be continued indefinitely from cuttings. In the 2n and 4n condition of absolutely homozygous genotypes, there is an exceptionally good genetic basis for selection problems.