Breeding of the cultivated potato species Solanum x juzepczukii Buk. and Solanum x curtilobum Juz. etBuk.

Abstract

This study investigated the possibility of recombining anew the genomes of the wild and cultivated progenitors of triploid S. juzepczukii and pentaploid S. curtilobum by following the known evolutionary pathway of these two species. Before starting the actual breeding work, the natural variation of S. juzepczukii, S. curtilobum and their wild progenitor S. acaule was studied from the point of view of morphology, quantitative and qualitative tuber glycoalkaloid content and frost resistance. The morphological study was supplemented by a study of the soluble tuber proteins employing polyacrylamide slab-electrophoresis. From 137 accession of S. juzepczukii only 19 morphotypes were identified, 18 of which were also different in their protein spectra. The only red-tubered S. juzepczukii revealed a protein spectrum identical to that of the largest white-tubered group. On phylogenetic grounds, the occurrence of a red-tubered S. juzepczukii cannot be explained. It is concluded that this red clone is a somatic mutant for tuber colour which arose from a whitetubered clone. S. curtilobum was restricted in its variation to just two morphotypes differing only in tuber colour which are, however, identical chemotypes. This would be the case if one of the clones was a somatic mutant for tuber colour from the other one. The glycoalkaloids α-solanine, α-chaconine, tomatine, demissine and α- and β-solamarine are shown to be useful taxonomic characters which confirm earlier hypotheses on the origin of S. juzepczukii and S. curtilobum. Laboratory tests showed the two cultivated species to be resistant to about −3°C whereas S. acaule is resistant to temperatures sometimes below−5°C. The diploid progenitor of S. juzepczukii, S. stenotomum, also has forms resistant to −3°C. The results of this study demonstrate that the proposed breeding scheme is possible.