Abstract
A monohaploid (x = 12) of Solanum tuberosum, its colchidiploid and their 2n parent clone have been cytologically examined. The meiotic analysis of the monoploid shows a certain degree of pairing at pachytene with a high frequency of bivalents at metaphase I. The bivalent frequency ranges from 2.07 to 3.0 per pollen mother cell (PMC). The most frequent classes are 3II + 6I and 2II + 8I. Several PMCs show secondary associations. At anaphase I (AI), the chromosomes distribute frequently in groups of 7 to 5 (32% of PMCs) and 6 to 6 (30% of PMCs). Occasionally, however, both disjunct chromosomes and univalents remain at the equatorial plane and divide with or without segregation, resulting in the formation of dyads or monads. The PMCs with a regular AI show a parallel orientation of spindles as well as a normal one, a situation that ends at telophase II with dyads, triads, and tetrads but 0% pollen fertility. The overall frequency of monads, dyads, triads, and tetrads is equal to 13, 69, 7 and 11%, respectively. Both in the parent clone and in the 2n colchidiploid clone, chromosome pairing is normal. The pairing behaviour in the monohaploid suggests the presence of duplicated sequences in the chromosome complement. An alteration of genes controlling the level of pairing is excluded.Key words: monohaploid, colchidiploid, chromosome pairing, meiosis.
Published Version
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