The Value of Diploid Peanut Relatives for Breeding and Genomics

Abstract

Collection, evaluation, and introgression research has been conducted with Arachis species for more than 60 years. Eighty species in the genus have been described and additional species will be named in the future. Extremely high levels of disease and insect resistances to immunity have been observed in many species of the genus as compared to the cultivated peanut, which makes them extremely important for crop improvement. Many thousands of interspecific hybrids have been produced in the genus, but introgression has been slow because of genomic incompatibilities and sterility of hybrids. Genomics research was initiated during the late 1980s to characterize species relationships and investigate more efficient methods to introgress genes from wild species to A. hypogaea. Relatively low density genetic maps have been created from inter-and intra-specific crosses, several of which have placed disease resistance genes into limited linkage groups. Of particular interest is associating molecular markers with traits of interest to enhance breeding for disease and insect resistances. Only recently have sufficiently large numbers of markers become available to effectively conduct marker assisted breeding in peanut. Future analyses of the diploid ancestors of the cultivated peanut, A. duranensis and A. ipaensis, will allow more detailed characterization of peanut genetics and the effects of Arachis species alleles on agronomic traits. Extensive efforts are being made to create populations for genomic analyses of peanut, and introgression of genes from wild to cultivated genotypes should become more efficient in the near future.

Utilizing Wild Species for Peanut Improvement

“…This is especially important in peanut because of the few progenies obtained during sterile or semisterile generations of selfing, and recombination between genomes appears to be at a relatively low frequency (Holbrook and Stalker, 2003). Attempts to use molecular markers to link with genes of interest have been evolving since the 1980s (Stalker et al, 2013), and microsatellite or SSR markers have become the assay of choice for genetic studies in Arachis because they are multiallelic, codominant, transferable among related species, PCRbased markers, and usable in tetraploid genomes. Efforts by several research groups to develop microsatellite markers for peanut have resulted in >9000 SSRs (Guo et al, 2016) and has enabled the phylogenetic evaluation of the genus Arachis (Krishna et al, 2004;Barkley et al, 2007;Tang et al, 2007;Varshney et al, 2009b;Moretzsohn et al, 2013) and production of moderately dense genetic maps for cultivated peanut.…”

The Use of Crop Wild Relatives in Maize and Sunflower Breeding

“…Some biological variables may increase both the need for expanded variation and the ease with which the expanded variation may be tapped. In more recent allopolyploid species, which often suffer from a severe genetic bottleneck, synthetic populations that recreate the interspecific cross can be used to bring all the variation still present in the wild ancestral species (and there are generally several species) to the domesticated gene pool, as has been done with wheat ( Triticum aestivum L.; Ogbonnaya et al, 2013) and peanut ( Arachis hypogaea L.; Stalker et al, 2013). More recent domesticates may cross more easily with their ancestral species, and successful introgression from wild to domesticated species for tomatoes ( Solanum lycopersicum L. = Lycopersicon escuelentum Mill), potatoes ( Solanum tuberosum L.), and sunflowers is common.…”

The Orphan Legume Genome Whose Time Has Come: Symposium Highlights from the American Peanut Research & Education Society Annual Meeting

“…Detailed papers originating from three speakers in the Symposium are published in this issue and recap the utilization of wild Arachis species in breeding (Stalker et al 2013), population development in cultivated peanut (Holbrook et al 2013b) and the history of the Peanut Genome Project along with the status of genetic mapping in peanut (Guo et al 2013). Peanut now has ''graduated'' from a position of orphan crop to one that soon will be replete with genetic and genomic resources .…”

“…Tom Stalker, North Carolina State University, reviewed the status of wild-species germplasm collections, resistance attributes, taxonomic relationships, crossability, and molecular variation (Stalker et al 2012(Stalker et al , 2013. Molecular variation between cultivated and wild species is much greater than between accessions within the cultivated species; therefore, genome sequence will obtain highly effective application for monitoring introgression of wild chromosome segments in breeding (Chu et al, 2011;Nagy et al, 2010).…”

“…Finally, the breadth of the peanut genome project to encompass wild diploid as well as cultivated tetraploid species, paralleled by renewed interest in utilizing diploid genetic resources to mine for allelic diversity (Bertioli et al, 2011;Stalker et al 2012Stalker et al , 2013, will promote the use of wild genetic resources in breeding through introgression pathways (Favero et al, 2006;Simpson, 2001). Tom Stalker, North Carolina State University, reviewed the status of wild-species germplasm collections, resistance attributes, taxonomic relationships, crossability, and molecular variation (Stalker et al 2012(Stalker et al , 2013.…”