The Phylogenetic Relationships of the Species within the Section Arachis Utilizing a Fatty Acid Synthesis Gene

Abstract

The original ancestors of the cultivated peanut (Arachis hypogaea), an allotetraploid, have not been conclusively determined, although several wild diploid species have been suggested. To identify the wild progenitors and to study the phylogenetic relationship of the species in the section Arachis, the sequence of a specific peanut gene was utilized. A cDNA of the fatty acid synthesis gene, stearoyl-ACP desaturase, was isolated and characterized. A region of this gene was then amplified from genomic DNA of nine wild species and sequenced. This sequence data, and the sequence information from the same region for the two cultivated peanut genes, were analyzed to determine the relatedness of the species. The results indicated that the cultivated peanut is derived from two separate lineages and supports the allopolyploid nature of the cultivated peanut. The amplified products were also digested with the Rsal restriction enzyme. A species-specific banding pattern unique to the DNA for some of the diploid species and one of the cultivated peanut genes was demonstrated. This technique provides a method for distinguishing diploid species and for analyzing gene expression in different tissues in the cultivated peanut.