Genomic affinities in Arachis section Arachis (Fabaceae): molecular and cytogenetic evidence

Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids ( x =10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic relationships in section Arachis , cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trn T-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic information supports earlier observations on genome types of A. cruziana , A. herzogii , A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis , A. hoehnei , A. ipaensis , A. palustris , A. praecox and A. williamsii . An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii . Sequence data of the trn T-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited genomic regions show promise in understanding genome types and relationships in Arachis .