Phylogenetic relationship between the tuberous Solanum species as revealed by restriction endonuclease analysis of chloroplast DNA.

Abstract

Cytoplasmic relationship between 37 tuberous Solanum accessions and hybrids and two Lycopersicon species was investigated by restriction fragment pattern analysis of chloroplast DNA using eight endonucleases. Variations found in their chloroplast DNAs were subjected to mutation analysis, from which a phylogenetic tree was constructed as shown in Fig. 4. The 30 species studied are classified into four groups from their chloroplast DNA similarities: (1) South American species and Mexican polyploid species, (2) Mexican diploid species, (3) S. etuberosum, and (4) S. lycopersicoides and Lycopersicon species. These groups correspond well to the groups established from crossability by Hawkes (1978). Cytoplasmic differences between 22 species in the first group are so small that these species seem to be of recent origin. Mexican diploid species in the second group greatly differ from those in the first group, and also from each other. S. etuberosum differs from all others by, at least, 21 mutational changes. S. lycopersicoides is rather closely related to the Lycopersicon species, and is different from other Solanum species by, at least, 21 mutational changes. Cytoplasms of all cultivated species except common potato, S. tuberosum ssp. tuberosum have originated monophyletically from S. stenotomum. The cytoplasm of common potato is revealed to have derived from Chilean tuberosum as pointed out by some workers, but the cytoplasm donor to Chilean tuberosum remains unidentified.