Relationships of the wild peanut species, section Arachis: A resource for botanical classification, crop improvement, and germplasm management.

Premise: Wild species are strategic sources of valuable traits to be introduced into crops through hybridization. For peanut, the 33 currently described wild species in the section Arachis are particularly important because of their sexual compatibility with the domesticated species, Arachis hypogaea. Although numerous wild accessions are carefully preserved in seed banks, their morphological similarities pose challenges to routine classification.

High-density bin-based genetic map reveals a 530-kb chromosome segment derived from wild peanut contributing to late leaf spot resistance.

Twenty-eight QTLs for LLS disease resistance were identified using an amphidiploid constructed mapping population, a favorable 530-kb chromosome segment derived from wild species contributes to the LLS resistance. Late leaf spot (LLS) is one of the major foliar diseases of peanut, causing serious yield loss and affecting the quality of kernel and forage. Some wild Arachis species possess higher resistance to LLS as compared with cultivated peanut; however, ploidy level differences restrict utilization of wild species.

Marker-assisted introgression of wild chromosome segments conferring resistance to fungal foliar diseases into peanut ( L.).

Introduction: Fungal foliar diseases can severely affect the productivity of the peanut crop worldwide. Late leaf spot is the most frequent disease and a major problem of the crop in Brazil and many other tropical countries. Only partial resistance to fungal diseases has been found in cultivated peanut, but high resistances have been described on the secondary gene pool.

Comparative repeatome analysis reveals new evidence on genome evolution in wild diploid Arachis (Fabaceae) species.

Opposing changes in the abundance of satellite DNA and long terminal repeat (LTR) retroelements are the main contributors to the variation in genome size and heterochromatin amount in Arachis diploids. The South American genus Arachis (Fabaceae) comprises 83 species organized in nine taxonomic sections. Among them, section Arachis is characterized by species with a wide genome and karyotype diversity.

Strong Resistance to Early and Late Leaf Spot in Peanut-Compatible Wild-Derived Induced Allotetraploids.

Early (ELS) and late leaf spots (LLS) are two of the most destructive diseases in peanut (). They can cause severe plant defoliation and tremendous yield loss in the absence of fungicide applications. The high costs of fungicides, their potential for deleterious effects on the environment, the tightening of regulations, and the development of fungicide resistance call for additional management strategies to mitigate both diseases.

Bulk RNA-Seq Analysis Reveals Differentially Expressed Genes Associated with Lateral Branch Angle in Peanut.

Lateral branch angle (LBA), or branch habit, is one of the most important agronomic traits in peanut. To date, the underlying molecular mechanisms of LBA have not been elucidated in peanut. To acquire the differentially expressed genes (DEGs) related to LBA, a TI population was constructed through the hybridization of a bunch-type peanut variety Tifrunner and prostrate-type Ipadur.

Development and Genetic Characterization of Peanut Advanced Backcross Lines That Incorporate Root-Knot Nematode Resistance From .

Crop wild species are increasingly important for crop improvement. Peanut ( L.) wild relatives comprise a diverse genetic pool that is being used to broaden its narrow genetic base.

TAR30, a homolog of the canonical plant TTTAGGG telomeric repeat, is enriched in the proximal chromosome regions of peanut (Arachis hypogaea L.).

Telomeres are the physical ends of eukaryotic linear chromosomes that play critical roles in cell division, chromosome maintenance, and genome stability. In many plants, telomeres are comprised of TTTAGGG tandem repeat that is widely found in plants. We refer to this repeat as canonical plant telomeric repeat (CPTR).

Spontaneous generation of diversity in Arachis neopolyploids (Arachis ipaënsis × Arachis duranensis)4x replays the early stages of peanut evolution.

Polyploidy is considered a driving force in plant evolution and domestication. Although in the genus Arachis, several diploid species were traditionally cultivated for their seeds, only the allotetraploid peanut Arachis hypogaea became the successful, widely spread legume crop. This suggests that polyploidy has given selective advantage for domestication of peanut.

Homoeologous recombination is recurrent in the nascent synthetic allotetraploid Arachis ipaënsis × Arachis correntina4x and its derivatives.

Genome instability in newly synthesized allotetraploids of peanut has breeding implications that have not been fully appreciated. Synthesis of wild species-derived neo-tetraploids offers the opportunity to broaden the gene pool of peanut; however, the dynamics among the newly merged genomes creates predictable and unpredictable variation. Selfed progenies from the neo-tetraploid Arachis ipaënsis × Arachis correntina (A.

Brazilian Kayabi Indian accessions of peanut, Arachis hypogaea (Fabales, Fabaceae): origin, diversity and evolution.

Peanut is a crop of the Kayabi tribe, inhabiting the Xingu Indigenous Park, Brazil. Morphological analysis of Xingu accessions showed variation exceeding that described for cultivated peanuts. This raised questions as to the origin of the Xingu accessions: are they derived from different species, or is their diversity a result of different evolutionary and selection processes? To answer these questions, cytogenetic and genotyping analyses were conducted.

Genotypic Characterization of the U.S. Peanut Core Collection.

Cultivated peanut () is an important oil, food, and feed crop worldwide. The USDA peanut germplasm collection currently contains 8,982 accessions. In the 1990s, 812 accessions were selected as a core collection on the basis of phenotype and country of origin.

Pod and Seed Trait QTL Identification To Assist Breeding for Peanut Market Preferences.

Although seed and pod traits are important for peanut breeding, little is known about the inheritance of these traits. A recombinant inbred line (RIL) population of 156 lines from a cross of Tifrunner x NC 3033 was genotyped with the Axiom_Arachis1 SNP array and SSRs to generate a genetic map composed of 1524 markers in 29 linkage groups (LG). The genetic positions of markers were compared with their physical positions on the peanut genome to confirm the validity of the linkage map and explore the distribution of recombination and potential chromosomal rearrangements.

A new source of root-knot nematode resistance from Arachis stenosperma incorporated into allotetraploid peanut (Arachis hypogaea).

Root-knot nematode is a very destructive pathogen, to which most peanut cultivars are highly susceptible. Strong resistance is present in the wild diploid peanut relatives. Previously, QTLs controlling nematode resistance were identified on chromosomes A02, A04 and A09 of Arachis stenosperma.

The genome sequence of segmental allotetraploid peanut Arachis hypogaea.

Like many other crops, the cultivated peanut (Arachis hypogaea L.) is of hybrid origin and has a polyploid genome that contains essentially complete sets of chromosomes from two ancestral species. Here we report the genome sequence of peanut and show that after its polyploid origin, the genome has evolved through mobile-element activity, deletions and by the flow of genetic information between corresponding ancestral chromosomes (that is, homeologous recombination).

Heterochromatin evolution in Arachis investigated through genome-wide analysis of repetitive DNA.

The most conspicuous difference among chromosomes and genomes in Arachis species, the patterns of heterochromatin, was mainly modeled by differential amplification of different members of one superfamily of satellite DNAs. Divergence in repetitive DNA is a primary driving force for genome and chromosome evolution. Section Arachis is karyotypically diverse and has six different genomes.

A Mechanism for Genome Size Reduction Following Genomic Rearrangements.

The factors behind genome size evolution have been of great interest, considering that eukaryotic genomes vary in size by more than three orders of magnitude. Using a model of two wild peanut relatives, and , in which one genome experienced large rearrangements, we find that the main determinant in genome size reduction is a set of inversions that occurred in , and subsequent net sequence removal in the inverted regions. We observe a general pattern in which sequence is lost more rapidly at newly distal (telomeric) regions than it is gained at newly proximal (pericentromeric) regions - resulting in net sequence loss in the inverted regions.

Comparative root transcriptome of wild Arachis reveals NBS-LRR genes related to nematode resistance.

Background: The Root-Knot Nematode (RKN), Meloidogyne arenaria, significantly reduces peanut grain quality and yield worldwide. Whilst the cultivated species has low levels of resistance to RKN and other pests and diseases, peanut wild relatives (Arachis spp.) show rich genetic diversity and harbor high levels of resistance to many pathogens and environmental constraints.

Segmental allopolyploidy in action: Increasing diversity through polyploid hybridization and homoeologous recombination.

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.

Introgression of wild alleles into the tetraploid peanut crop to improve water use efficiency, earliness and yield.

The introduction of genes from wild species is a practice little adopted by breeders for the improvement of commercial crops, although it represents an excellent opportunity to enrich the genetic basis and create new cultivars. In peanut, this practice is being increasingly adopted. In this study we present results of introgression of wild alleles from the wild species Arachis duranensis and A.

The genome structure of (Linnaeus, 1753) and an induced allotetraploid revealed by molecular cytogenetics.

Peanut, (Linnaeus, 1753) is an allotetraploid cultivated plant with two subgenomes derived from the hybridization between two diploid wild species, (Krapovickas & W. C. Gregory, 1994) and (Krapovickas & W.

High-density genetic map using whole-genome resequencing for fine mapping and candidate gene discovery for disease resistance in peanut.

Whole-genome resequencing (WGRS) of mapping populations has facilitated development of high-density genetic maps essential for fine mapping and candidate gene discovery for traits of interest in crop species. Leaf spots, including early leaf spot (ELS) and late leaf spot (LLS), and Tomato spotted wilt virus (TSWV) are devastating diseases in peanut causing significant yield loss. We generated WGRS data on a recombinant inbred line population, developed a SNP-based high-density genetic map, and conducted fine mapping, candidate gene discovery and marker validation for ELS, LLS and TSWV.