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Genus Arachis comprises 82 species distributed into nine taxonomic sections. Most Arachis species are wild and those from Arachis section have been evaluated for many traits, since they can be used in peanut breeding. Most of the remaining species have been neglected and understudied. Recently, resveratrol content and expression of a resveratrol synthase gene were analyzed in wild Arachis species. Our aim was to expand the knowledge about resveratrol in Arachis, analyzing species from five sections and evaluating the expression of a resveratrol synthase (RS) gene responsive to ultraviolet light (UV) along the time. In a first experiment, the resveratrol content after UV induction was analyzed on detached leaves of 12 species from five sections. Variation was observed among species and accessions of the same species. The highest contents were found in A. lignosa (843.9 μg/g) and A. triseminata (745.4 μg/g). In a second experiment, RS expression and resveratrol content in four species and one synthetic amphidiploid were analyzed at 0, 7, 15 and 24 h pos induction (hpi) with UV. In most genotypes, the highest RS expression level was at 0 hpi, whereas the highest resveratrol content was at 15 hpi. Our results suggested that resveratrol is ubiquitously present in the genus Arachis with different capacities of synthesis among species and accessions in response to ultraviolet treatment. Presence of resveratrol in wild Arachis species adds new value to these genetic resources.

The use of wild species in peanut breeding provides remarkable opportunities for introducing new traits to the peanut crop and it has increased in recent years. Here, we report the morphological and agronomic, including disease resistance, variation observed in 87 Recombinant Inbred Lines (RILs) that were derived from the wild ancestors of peanut and the cultivar Runner IAC-886. These lines exhibited a wide range of variation for these traits, with transgressive segregation and novel phenotypes being observed in many lines. Quantitative Trait Loci (QTLs) for agronomic and resistance traits were detected. Six RILs with contrasting phenotypes for agronomic traits and moderate resistance to leaf spots were genotyped. All of the lines had, on average, 50% wild alleles, with at least one large wild segment and multiple interspersed alleles in all of the chromosomes. Genetic exchange between subgenomes was observed. On four lines, the top of Chr 05/15, which is tetrasomic AAAA in A. hypogaea, has been restored to its AABB state by the introgression of A. ipa&euml, nsis alleles. We identified lines with good agronomic traits while harboring genome composition and structure completely different from each other and from the cultivated peanut. The variation that is observed for the fruit type is also important for a better comprehension of the domestication process in peanut. This increase in genetic diversity has great potential benefits for the peanut breeding programs.

PREMISE OF THE STUDY The genetic bottleneck of polyploid formation can be mitigated by multiple origins, gene flow, and recombination among different lineages. In crop plants with limited origins, efforts to increase genetic diversity have limitations. Here we used lineage recombination to increase genetic diversity in peanut, an allotetraploid likely of single origin, by crossing with a novel allopolyploid genotype and selecting improved lines. METHODS Single backcross progeny from cultivated peanut × wild species-derived allotetraploid cross were studied over successive generations. Using genetic assumptions that encompass segmental allotetraploidy, we used single nucleotide polymorphisms and whole-genome sequence data to infer genome structures. KEY RESULTS Selected lines, despite a high proportion of wild alleles, are agronomically adapted, productive, and with improved disease resistances. Wild alleles mostly substituted homologous segments of the peanut genome. Regions of dispersed wild alleles, characteristic of gene conversion, also occurred. However, wild chromosome segments sometimes replaced cultivated peanut's homeologous subgenome; A. ipaensis B sometimes replaced A. hypogaea A subgenome (~0.6%), and A. duranensis replaced A. hypogaea B subgenome segments (~2%). Furthermore, some subgenome regions historically lost in cultivated peanut were "recovered" by wild chromosome segments (effectively reversing the "polyploid ratchet"). These processes resulted in lines with new genome structure variations. CONCLUSIONS Genetic diversity was introduced by wild allele introgression, and by introducing new genome structure variations. These results highlight the special possibilities of segmental allotetraploidy and of using lineage recombination to increase genetic diversity in peanut, likely mirroring what occurs in natural segmental allopolyploids with multiple origins.