Synaptic mutants in potato, Solanum tuberosum L. I. Expression and identity of genes for desynapsis

For tuber-bearing Solanum species, six monogenic recessive synaptic mutants, designated sy-1, sy-2, sy-3, sy-4, ds, and dsc have been reported in the literature. In the present investigation no indication for the existence of the mutant sy-1, affecting megasporogenesis only, was found. The mutant ds was confirmed to display typical desynaptic behaviour in microsporogenesis and shown to similarly affect megasporogenesis. It furthermore proved to be allelic to the mutants sy-3 and dsc. It is proposed that the mutants sy-3, ds, and dsc be uniformly designated ds-1, whereas the remaining mutants sy-2 and sy-4 (possibly identical) may be designated simply as synaptic mutant until their actual identity has been established. The observed F1 segregations generally support monogenic recessive inheritance of ds-1. However, in one cross progeny the expected mutant phenotype was not clearly expressed in contrast with its reciprocal, which might indicate cross-specific influence of the cytoplasm on ds-1 expression. The potential value and limitations of desynaptic (ds-1ds-1) mutants for potato breeding and true potato seed production are discussed.Key words: Solanum, (de)synaptic mutants, microsporogenesis, megasporogenesis, 2n gametes.