Abstract: Euploidic variation in filial generation of spontaneous triploid Allium tuberosum Rottler ex Spreng. was studied in this paper. Spontaneous triploid A.tuberosum is highly sterile because of the difficulties involved in chromosome pairing and disjunction during meiosis. Its ex-pected value of fertility is only 1/8192, but the practical value of fertility is 1 / 5882. It is higher than its expected one. The plants in filial generation of the triploid with a basic haploid number of 8, have members with chromosome numbers of 16, 24 and 32. The karyotypes of these plants were analysed. Their karyotype formulas are 2n = 2x = 16 = 14m + 2st(SAT), 2n = 3x = 24 = 21m + 3st(SAT), 2n=4x=32=28m + 4st(SAT). They are diploid, triploid and tetraploid respectively, and have become a euploidic series. Three kinds of euploid are in a ratio of 13 diploids: 20 triploids: 12 tetraploids. It approximately coincides with expected ratio of 1: 2: 1. It is proved that this spontaneous triploid A. tuberosum is an autotriploid.

Key words: Allium tuberosum