EVOLUTION OF CYTOPLASMIC FACTORS IN TETRAPLOID CULTIVATED POTATOES (SOLANACEAE)

Abstract

Analyses were made, by study of reciprocal crosses, of cytoplasmic factors of Solanum tuberosum ssp. andigena and S. tuberosum ssp. tuberosum including both northern hemipshere cultivated clones and clones from Chiloe Archipelago in Coastal Chile. The purpose was to compare the cytoplasmic factors of these three sorts of S. tuberosum with those of their diploid ancestors and with one another as aids in determining their positions on pathways of evolutionary descent. Preliminary to making the comparisons it was shown that the cytoplasm‐chromosomal gene interaction that produces deformed flowers in diploid forms of Solanum functions also in induced autotetraploids, with deformed flowers being expressed in [df8]‐dfdfdfdf individuals. Plants of the S. stenotomum‐phureja complex, putative ancestors of S. tuberosum ssp. andigena, were known from earlier work to have the [df8] plasmon factor, but ssp. andigena itself was found to lack it. A newly discovered cytoplasmic abnormality, anther‐lobe overlap, is expressed in plants having plasmon factor [lo8] and homozygous for recessive alleles lo. The [lo8] plasmon factor is present in S. phureja and in S. tuberosum ssp. andigena. Altogether, ssp. andigena potatoes match their putative stenotomum‐phureja ancestors in eight of the nine plasmon factors identified to date, differing with them only in the lack of [df8]. Northern hemisphere and Chiloe clones of S. tuberosum ssp. tuberosum lack the [df8] and the [lo8] plasmon factors. Chiloe clones are identical to northern hemisphere cultivated ones in all eight plasmon factors for which they were tested. Both contrasted with ssp. andigena, their putative ancestor, in eight of nine factors tested, resembling it only in their common lack of [df8]. The evidence supports the idea that clones cultivated now in the northern hemisphere are descendants of direct imports from coastal Chile. The clone Rough Purple Chili was an example of an imported clone that became important in potato breeding, but it has not been clear whether it was brought from Chile or from Andean regions of northern South America. The leaf form and cytoplasmic factors of Garnet Chili, a first generation derivative of Rough Purple Chili, were found to be those of S. tuberosum ssp. tuberosum. Rough Purple Chili is, therefore, an example of such direct importation from Chile.