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Volume 15, Issue 3 p. 562-572
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Registration of three peanut allotetraploid interspecific hybrids resistant to late leaf spot disease and tomato spotted wilt

Ye Chu

Ye Chu

Horticulture Dep., Univ. of Georgia, Tifton, GA, 31793 USA

Contribution: Conceptualization, Data curation, Methodology, Writing - original draft

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H. Thomas Stalker

H. Thomas Stalker

Dep. of Crop and Soil Sciences, North Carolina State Univ., Raleigh, NC, 27695 USA

Contribution: Conceptualization, Data curation, Writing - review & editing

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Kathleen Marasigan

Kathleen Marasigan

Horticulture Dep., Univ. of Georgia, Tifton, GA, 31793 USA

Contribution: Data curation, Writing - review & editing

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Chandler M. Levinson

Chandler M. Levinson

Horticulture Dep., Univ. of Georgia, Tifton, GA, 31793 USA

Institute of Plant Breeding, Genetics and Genomics, Univ. of Georgia, Athens, GA, 30602 USA

Contribution: Data curation, Writing - review & editing

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Dongying Gao

Dongying Gao

Dep. of Crop and Soil Science, Univ. of Georgia, Athens, GA, 30602 USA

Contribution: Data curation, Writing - review & editing

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David J. Bertioli

David J. Bertioli

Institute of Plant Breeding, Genetics and Genomics, Univ. of Georgia, Athens, GA, 30602 USA

Dep. of Crop and Soil Science, Univ. of Georgia, Athens, GA, 30602 USA

Contribution: Conceptualization, Writing - review & editing

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Soraya C. M. Leal-Bertioli

Soraya C. M. Leal-Bertioli

Institute of Plant Breeding, Genetics and Genomics, Univ. of Georgia, Athens, GA, 30602 USA

Dep. of Plant Pathology, Univ. of Georgia, Athens, GA, 30602 USA

Contribution: Conceptualization, Writing - review & editing

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C. Corley Holbrook

C. Corley Holbrook

USDA–ARS, Crop Genetics and Breeding Research Unit, Tifton, GA, 31793 USA

Contribution: Conceptualization, Data curation, Writing - review & editing

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Scott A. Jackson

Scott A. Jackson

Institute of Plant Breeding, Genetics and Genomics, Univ. of Georgia, Athens, GA, 30602 USA

Dep. of Crop and Soil Science, Univ. of Georgia, Athens, GA, 30602 USA

Contribution: Conceptualization, Writing - review & editing

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Peggy Ozias-Akins

Corresponding Author

Peggy Ozias-Akins

Horticulture Dep., Univ. of Georgia, Tifton, GA, 31793 USA

Institute of Plant Breeding, Genetics and Genomics, Univ. of Georgia, Athens, GA, 30602 USA

Correspondence

Peggy Ozias-Akins, Horticulture Dep., Univ. of Georgia, Tifton, GA 31793, USA.

Email: [email protected]

Contribution: Conceptualization, Funding acquisition, Project administration, Supervision, Writing - review & editing

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First published: 20 August 2021
Citations: 3

Assigned to Associate Editor Naveen Puppala.

Registration by CSSA.

Abstract

Cultivated peanut (Arachis hypogaea L.) has a narrow genetic base and is isolated from its wild relatives. This genetic bottleneck results in a lack of strong resistance to biotic and abiotic stress. However, high levels of genetic variation and resistance exist among the wild relatives. In order to enlarge the genetic base of cultivated peanut and introgress beneficial alleles from the wild relatives, interspecific hybrids were produced among a set of selected diploid species. Upon colchicine treatment, fertile allotetraploids were recovered from three combinations including (A. ipaënsis KG 30076  × A. correntina GKP 9530)4x (Reg. no. GP-241, PI 695391), (A. ipaënsis KG 30076 × A. duranensis KGBSPSc 30060)4x (Reg. no. GP-242, PI 695392), and (A. valida KG30011 × A. stenosperma V 10309)4x (Reg. no. GP-243, PI 695393). All of them demonstrated high levels of resistance to leaf spot diseases in the field. Tolerance to Tomato spotted wilt virus was found in (A. valida KG 30011 × A. stenosperma V 10309)4x. These newly created allotetraploids are cross-compatible with cultivated peanut. These genetic resources will provide peanut breeding researchers with new sources of disease resistances to improve the agronomic performance of cultivated peanut.

Abbreviations

  • AUDPC
  • area under the disease progress curve
  • IpaCor2-GA-NC
  • (A. ipaënsis KG 30076  × A. correntina GKP 9530)4x
  • IpaDur3-GA-NC
  • (A. ipaënsis KG 30076 × A. duranensis KGBSPSc 30060)4x
  • SNP
  • single nucleotide polymorphism
  • TSWV
  • Tomato spotted wilt virus
  • ValSten1-GA-NC
  • (A. valida KG 30011 × A. stenosperma V 10309)4x .
  • 1 INTRODUCTION

    Peanut (Arachis hypogaea L.) is an important oil crop in temperate growing regions, and 33 million ha was dedicated to peanut production throughout the world in 2018 (FAO, 2018). These diverse growing environments impose varied biotic and abiotic stresses on peanut farming. Cultivated peanut is an allotetraploid (AABB; 2= 4= 40) arising from possibly a single polyploidization event of a diploid interspecific hybrid between A. ipaënsis (BB; 2= 2= 20) and A. duranensis (AA; 2= 2= 20) (Bertioli et al., 2016, 2019; Kochert et al., 1996). The doubled genome size in peanut resulted in an increase in fruit size and many other agronomic characteristics, which attracted humans to cultivate and disseminate peanut as a crop. However, ploidy differences between the cultivated peanut and its more than 30 wild diploid relatives in the Arachis section result in crossing barriers and limited genetic exchange, leading to a narrowed base for peanut (Krapovickas et al., 2007). In cultivated peanut, there is a lack of stable resistance to a number of economically important peanut diseases and pests such as root-knot nematode (Holbrook & Noe, 1992; Holbrook et al., 2000), rust (caused by Puccinia arachidis Speg.) (Subrahmanyam et al., 1989), leaf spots [caused by Passalora arachidicola (Hori) and Nothopassalora personata (Berk. & M.A. Curtis)] (Holbrook & Anderson, 1995), Aspergillus flavus (the causal agent of aflatoxin production) (Holbrook et al., 2009), bacterial wilt [caused by Pseudomonas solanacearum (Smith) Smith] (Liao, 2017), fall armyworm, and thrips (Lynch, 1990). Conversely, diploid wild species possess a wide range of resistances to these pests and diseases (Stalker, 2017; Stalker et al., 2013). Introgression of alleles from diploid species to cultivated peanut introduced immunity to root knot nematode (Holbrook et al., 2008; Nagy et al., 2010; Simpson et al., 1993, 2003), resistance to leaf spots and rust (Clevenger et al., 2017a; Company et al., 1982; Pandey et al., 2017; Stalker et al., 1993; Tallury et al., 2014), improved seed and pod characteristics (Fonceka et al., 2012), and drought tolerance (Dutra et al., 2018). Several of these materials were released as improved germplasm lines for nematode or leaf spot disease resistance and were used to develop disease-resistant cultivars (Holbrook et al., 2017; Simpson & Starr, 2001; Simpson et al., 2003).

    Continued efforts to introduce beneficial genes from wild species are needed, to combat not only common pathogens and pests of peanut but also emerging diseases such as peanut smut (caused by Thecaphora frezii) (Rago et al., 2017). In this study, three fertile synthetic allotetraploid interspecific hybrids (A. ipaënsis KG 30076  × A. correntina GKP 9530)4x (IpaCor2-GA-NC, Reg. no. GP-241, PI 695391), (A. ipaënsis KG 30076 × A. duranensis KGBSPSc 30060)4x (IpaDur3-GA-NC, Reg. no. GP-242, PI 695392), and (A. valida KG 30011 × A. stenosperma V 10309)4x (ValSten1-GA-NC, Reg. no. GP-243, PI 695393) were created through interspecific hybridization and colchicine treatment of the original diploid hybrids. The choice of diploid species was based on their cross-compatibility and their diverse range of resistances to multiple diseases and insect pests (Supplemental Table S1).

    Core Ideas

    • These hybrids can broaden the genetic base of cultivated peanut by introgression.
    • New synthetic allotetraploids from peanut wild relatives carry disease resistance.
    • Synthetic allotetraploids are cross-compatible with cultivated peanut.

    In order to explore the utility of these new allotetraploids, field tests for resistance to leaf spots and Tomato spotted wilt virus (TSWV) were performed in this study. Early and late leaf spot diseases cause defoliation during the pod-filling stage of peanut growth. Reduction in photosynthesis leads to poor grade and up to 70% yield loss (Singh et al., 2011). The cost of fungicide programs to control leaf spots ranked at the top for peanut farm management costs (Woodward et al., 2014). Tomato spotted wilt virus, a viral disease vectored by thrips, severely stunts the growth of plants early in the growing season and causes a high yield penalty. Peanut production in Georgia was devastated in the 1990s due to the lack of host resistance (Culbreath & Srinivasan, 2011). Afterwards, tolerance or resistance to TSWV became a prerequisite for peanut cultivars released in southeastern growing regions. Retention of TSWV resistance alleles from PI 203396 in modern cultivars through breeding and selection (Branch, 1996; Clevenger et al., 2017b; Gorbet et al., 2008) secured the hectarage of peanut in this region, which accounted for more than 50% of U.S. peanut production in 2019 (www.nationalpeanutboard.org/). Due to the potential breakdown of established host resistance, multiple genetic sources of host resistance are needed to ensure sustainable peanut production. High levels of resistance to leaf spots and tolerance to TSWV were identified in these synthetic allotetraploids, suggesting the potential use of these genetic resources to improve host resistance in cultivated peanut.

    2 METHODS

    2.1 Generation of allotetraploid interspecific hybrids

    Interspecific hybridization was performed among the diploid species with B-genome diploid species A. ipaënsis KG 30076 (PI 468322) and A. valida KG 30011 (PI 468154) as female parents and the A-genome diploid species A. correntina GKP 9530 (PI 262808), A. duranensis KGBSPSc 30060 (PI 468197), or A. stenosperma V 10309 (PI 666100) as male parents yielding sterile F1 hybrids. Sterility of the diploid hybrids was confirmed by pollen staining using Alexander blue (Alexander, 1969). Species information is provided in Table 1. It was shown that the BB × AA combination was most conducive for allotetraploid production (Favero et al., 2006). Sterility of F1 interspecific hybrids was confirmed by pollen staining and all of the hybrids were propagated by cuttings. Colchicine treatment was applied to all combinations to double the chromosomes and restore fertility. The method of colchicine treatment followed Favero et al. (2006) with minor modifications. The 10-cm-long cuttings from diploid hybrids were immersed in 0.02% colchicine for 10 h before rooting in the Promix medium (Premier Tech Horticulture). Seeds harvested from the colchicine-treated sterile diploids could only have developed from somatically doubled tissues or unreduced gametes. Seed increase of these synthetic allotetraploids was performed in the greenhouse and the field. Seeds harvested from the colchicine-treated cuttings were called S0 seeds. Plants germinated from S0 seeds were called S0 plants. Seeds harvested from S0 plants were called S1 seeds and so forth. S2 seeds harvested from greenhouse-advanced S1 plants were used for the field tests.

    TABLE 1. Species information for the synthetic allotetraploids
    Synthetic allotetraploid Designation Genome composition A-genome parent A-genome parent PI no. B-genome parent B-genome parent PI no.
    (A. ipaënsis KG 30076 × A. correntina GKP 9530)4x IpaCor2-GA-NC BBAA A. correntina 9530 262808 A. ipaensis KG 30076 468322
    (A. ipaënsis KG 30076 × A. duranensis KGBSPSc 30060)4x IpaDur3-GA-NC BBAA A. duranensis 30060 468197 A. ipaensis KG30076 468322
    (A. valida KG 30011 × A. stenosperma V10309)4x ValSten1-GA-NC BBAA A. stenosperma V10309 666100 A. valida KG 30011 468154

    2.2 Field tests for TSWV and leaf spot resistance

    Both field studies were conducted in Tifton, GA, following a complete randomized block design with three replicates. Each plot was 3 m long, consisting of two rows. A 1.5-m-wide alley separated the plots. Peanut cultivars with known resistance and susceptibility to both diseases were included as controls. For the TSWV test, ‘NC 94022’ (Culbreath et al., 2005) and ‘TifNV-High O/L’ (Holbrook et al., 2017) were resistant controls, whereas ‘Gregory’ (Isleib et al., 1999) and ‘Florunner’ (Norden, et al., 1969) were susceptible controls. Control lines were planted by direct seeding on 11 Apr. 2019. Due to the concerns of seed dormancy and low survival rate upon direct seeding for the allotetraploids, seeds were germinated in Jiffy pots in the greenhouse on 2 April and transplanted to the field on 25 April. The field was irrigated before and after transplanting. The crop was managed with standard practices including fungicide sprays; however, pesticide application was withheld. The TSWV disease ratings were taken on 123 and 129 d after planting. The percentage of the canopy demonstrating TSWV symptoms was documented for each plot, with 0% indicating no TSWV symptoms and 100% indicating the whole plot exhibited TSWV symptoms. To reduce the bias of visual rating, two ratings performed by the same personnel at the end of the season were taken. The mean value of the two ratings was used to represent the disease response of each synthetic allotetraploid.

    For the leaf spot field test, IAC322, ‘Georganic’ (Holbrook & Culbreath, 2008), and ‘GP-NC WS 16’ (Tallury et al., 2014) served as resistant controls. Gregory (Isleib et al., 1999) and Runner 886 were included as susceptible controls. The control lines were planted on 22 May 2019 and the allotetraploids were germinated in the greenhouse on 16 May and transplanted on 6 June. Fungicides were withheld throughout the season. The Florida 1–10 scale (Knauft et al., 1988) was used to document leaf spot disease severity on 102, 112, 122 and 133 d after planting. Daily area under the disease progress curve (AUDPC) was calculated to quantify the disease response.

    2.3 Pod and seed characteristics

    The peg strength of these synthetic allotetraploid interspecific hybrids is weaker than that of cultivated peanut (Levinson et al., 2021a). In the majority of hybrids, two seeds were formed per pod and the apical seed was connected to the basal seed through a long and fragile isthmus, rendering mechanized harvest ineffective for these materials. Therefore, the plots in both the TSWV and leaf spot tests were manually dug and picked. The 100-pod weight, 100-seed weight, and total yield were documented from the TSWV field test. Seed width and seed length were measured using ASSESS software Version 2.0 (Lamari, 2008) with a U.S. quarter as the calibrator.

    2.4 Genotyping and phylogenetic analysis

    The S0 individuals from the allotetraploids and 19 cultivars and germplasm lines were genotyped. Among the 19 cultivated peanut lines, four belong to the subspecies fastigiata and the remaining 15 to subspecies hypogaea. All of the plants were grown in the greenhouse, and DNA was extracted from young leaves using a Qiagen DNeasy plant mini kit (Thermofisher Scientific) and genotyped by the Axiom_ Arachis SNP array version 2 (Thermofisher Scientific) (Clevenger et al., 2018; Korani et al., 2019). Single nucleotide polymorphism (SNP) calling was performed with Axiom Analysis Suite (Version 1.1, Thermofisher Scientific). A phylogenetic tree was constructed with the SNPhylo program using the default settings (Lee et al., 2014).

    2.5 Statistical analysis

    Analysis of variance was performed with SAS Enterprise Guide software Version 6.1 (SAS Institute) to determine the genotypic effect on the measured traits, and the means were separated by Tukey's test (p < .05).

    3 CHARACTERISTICS

    All three synthetic allotetraploid lines have prominent main stems, and the laterals are decumbent with a highly spreading growth habit (Figure 1). The field design allowed the formation of a dense canopy from the allotetraploids, which covered most of the beds and provided a conducive environment for late leaf spot disease evaluation. Flowers were profusely produced on all allotetraploids. IpaCor2-GA-NC had orange-colored flowers, whereas IpaDur3-GA-NC and ValSten1-GA-NC had yellow flowers. The morphological traits of these synthetic allotetraploids, including mainstem height, primary lateral length, internode length, flower counts, flower banner and wing sizes, hypanthium length, flower color, leaf size, leaf hairiness, plant size, pod and seed sizes, etc., were measured (Levinson et al., 2021b). These allotetraploid lines are cross-compatible with cultivated peanut. We successfully made crosses and backcrosses using the allotetraploid lines as pollen donors and elite cultivars as the recurrent female parents.

    Details are in the caption following the image
    Three allotetraploid interspecific hybrids grown at the Gibbs Farm, Tifton, GA, in 2019: (a) IpaCor2-GA-NC; (b) IpaDur3-GA-NC; (c) ValSten1-GA-NC; and (d) ‘Florida-07’, a cultivated runner-type peanut serving as a check

    Pods harvested from allotetraploid interspecific hybrids were mostly single-seed or broken single-seed pod segments. This is due to the fragility of the long and thin isthmus separating the seeds in double-seeded pods. All hybrids had deep pod reticulation and prominent beaks (Figure 2). The yield of these lines ranged from 7 to 115 g per plot, which was much less than cultivars that yielded at least 2 kg per plot. The seed and pod sizes were similar among the allotetraploids and only reached 20–30% of the size of TifNV-High O/L (Holbrook et al., 2017), a recently released runner-type cultivar (Figure 3a). Since the double-seeded pods were predominant and selected to measure the 100-pod weight of TifNV-High O/L, the 100-pod weight of this cultivar was more than twice that of its 100-seed weight. On the other hand, most of the pods harvested from the allotetraploids were single-seeded pod segments; therefore, the difference between 100-pod weight and 100-seed weight for each of the allotetraploids was much less. As for the shape of the seeds measured by the seed length/width ratio, IpaCor2-GA-NC was significantly more slender in shape than TifNV-High O/L (Figure 3b).

    Details are in the caption following the image
    Pods and seeds from the allotetraploid interspecific hybrids: (a) IpaCor2-GA-NC; (b) IpaDur3-GA-NC; and (c) ValSten1-GA-NC
    Details are in the caption following the image
    Pod and seed measurements: (a) 100 mature pod weight and 100 mature seed weight and (b) seed length/width ratio. TifNV-High O/L is a cultivar control. Bars above data columns represent standard error. Different letters on top of the bars indicate statistically significant differences in the grouping at p < .05

    The pod and seed characteristics of these allotetraploid interspecific hybrids were similar to previous reports (Leal-Bertioli et al., 2014). Although chromosome doubling restored the fertility and resulted in pod and seed production, the pod size of these new allotetraploids remained much smaller than cultivated peanut, as previously reported (Leal-Bertioli et al., 2014, 2017).

    The early planting of the TSWV field test resulted in severe TSWV disease pressure (Figure 4). The control susceptible lines, Florunner and Gregory, had 82 and 57%, respectively, of the canopy symptomatic for TSWV infection. All of the allotetraploids had numerically lower percentages of TSWV-infected canopy than the susceptible controls. ValSten1-GA-NC was statistically more resistant to TSWV than the susceptible lines. The most resistant line was the cultivated check NC 94022 (Culbreath et al., 2005). Tomato spotted wilt virus, vectored by thrips, infects more than 1,000 plant species including both monocots and dicots (Parrella et al., 2003). As an RNA virus, TSWV belongs to the Tospovirus genus and harbors high levels of genetic variability due to error-prone replication (Domingo & Holland, 1997). Population genetic studies confirmed that TSWV is genetically diverse, and selection pressure shapes the population structure of the virus (Kaye et al., 2010; Tsompana et al., 2005). The complex virus–vector–host interaction imposes strong challenges for field disease management (Culbreath & Srinivasan, 2011). Therefore, integrating multiple sources of host resistance in cultivated peanut is of importance to provide durable suppression of TSWV infection. ValSten1-GA-NC identified in this study offers another potential resistance source for peanut breeders to utilize and improve the durability of resistance against TSWV.

    Details are in the caption following the image
    Allotetraploid interspecific hybrids demonstrated tolerance to Tomato spotted wilt virus (TSWV) in the 2019 field test. Bars above data columns represent standard error. Different letters mark the statistically significant differences in the grouping at p < .05

    The late planting date of the leaf spot field study maximized the leaf spot disease pressure (Figure 5a). The susceptible controls, Gregory (Isleib et al., 1999) and Runner 886, reached Florida scale ratings of 8 and 9, respectively, indicating complete infection by leaf spots on the canopy and greater than 75% defoliation caused by the fungal infection during the late season. The resistant cultivated controls, Georganic (Holbrook & Culbreath, 2008), GP-NC WS 16 (Tallury et al., 2014), and IAC 322 demonstrated significantly higher levels of resistance than the susceptible checks. However, these moderately resistant cultivated lines had the daily AUDPC of 4–6 due to the emergence of leaf spot lesions on the top of the canopy accompanied by noticeable defoliation (Knauft et al., 1988). On the other hand, the allotetraploid interspecific hybrids exhibited almost no leaf spot symptoms or defoliation throughout the season (Figure 5a). The leaf tissues from the allotetraploids randomly collected at the end of the season were healthy compared with the leaves from the susceptible controls, which were yellowing and heavily infected with leaf spots (Figure 5b). These data suggest that all allotetraploid interspecific hybrids harbor high levels of resistance to late leaf spot, a globally prevalent disease plaguing peanut production. Two resistant checks, GP-NC WS 16 and IAC 322, are derivative lines from the interspecific hybrids initially created at North Carolina State University (Company et al., 1982) and have several wild chromosomal segments from A. cardenasii, an A-genome diploid species (Clevenger et al., 2017a). The contribution of late leaf spot resistance on IAC 322 from A. cardenasii introgressed regions was confirmed recently (Lamon et al., 2020). There is no known resistance to leaf spot diseases in cultivated peanut. The high levels of resistance to late leaf spot in these allotetraploid interspecific hybrids offer the peanut breeding community novel genetic resources to breed for leaf spot resistance. The separation of disease response among the checks for both TSWV and leaf spots was consistent with previous field trials (Chu et al., 2019; Khera et al., 2016). Therefore, the field test conducted in 2019 captured the typical level of disease pressure in southeastern Georgia. The data suggested that the resistance or tolerance detected in these allotetraploid interspecific hybrids is durable across environments in the U.S. peanut production regions affected by this pathogen. Late leaf spot was the predominant pathogen in the 2019 field test. Disease resistance against early leaf spot needs to be further tested in fields with high disease pressure from this fungal pathogen.

    Details are in the caption following the image
    Allotetraploid interspecific hybrid lines demonstrated very high levels of resistance to leaf spot (LS) diseases in a 2019 field test: (a) leaf spot disease ratings expressed as daily area under the disease progress curve (AUDPC), with different letters marking statistically significant differences in a grouping at p < .05; and (b) random leaf samples collected from the field at 126 d after planting: (1) IpaDur3-GA-NC, (2) ValSten1-GA-NC, (3) IpaCor2-GA-NC, and (4) Runner 886, the susceptible cultivated control

    Phylogenetic analysis was performed with 2,775 polyhigh-resolution SNP markers from the Arachis SNP array. Clear separation of clusters between the new allotetraploid interspecific hybrids and cultivated peanut was illustrated in the phylogenetic tree (Figure 6). Most of the cultivated lines belong to the subspecies hypogaea, grouped in one clade, and diverged from the four fastigiata lines supporting the validity of this analysis. SSD 6 is in the botanical variety of hirsuta and NC 94022 is a breeding line derived from SSD 6 (Culbreath et al., 2005). Separation of these two lines from the rest in the botanical variety of hypogaea is expected. Among the allotetraploids, IpaDur3-GA-NC was closest to the cultivated peanut, yet it formed a separate clade from the cultivated peanut. ValSten1-GA-NC and IpaCor2-GA-NC fell in separate clades and both were distant from the cultivated and IpaDur3-GA-NC clade. The two progenitors of cultivated peanut are A. ipaënsis and A. duranensis (Bertioli et al., 2016; Kochert et al., 1996). There is only one accession of A. ipaënsis and 51 accessions of A. duranensis (Krapovickas et al., 2007) described in the U.S. germplasm collection. Arachis duranensis 30060 used in our study is a different accession from the accession most likely to have produced cultivated peanut (Bertioli et al., 2019). Regardless, the higher level of relatedness of IpaDur3-GA-NC with cultivated peanut compared with the other allotetraploids confirms previous findings concerning the origin of peanut.

    Details are in the caption following the image
    Phylogenetic tree of the allotetraploid interspecific hybrids and cultivated peanuts. Allotetraploid interspecific hybrids are in black font. Cultivated peanut lines that belong to subspecies hypogaea are in green font and marked with †. Cultivated peanut lines that belong to subspecies fastigiata are in orange font with *.

    Beneficial traits of these new allotetraploids are not limited to resistance to late leaf spot and TSWV. We observed potential rust resistance among these materials as well. However, testing additional traits requires further study. Releasing these materials will allow the maintenance and distribution of these valuable genetic materials to the peanut breeding community, which will broaden the genetic base of cultivated peanut.

    4 AVAILABILITY

    Seed of IpaCor2-GA-NC, IpaDur3-GA-NC, and ValSten1-GA-NC have been deposited with the USDA Plant Genetic Resources and Conservation Unit (Griffin, GA) and the National Laboratory for Genetic Resources Preservation (Fort Collins, CO), and a limited number of seeds will be available for public distribution after publication of this release. Inquiries regarding availability of seed for research purposes or for commercial use should be sent to the corresponding author.

    ACKNOWLEDGMENTS

    This work was funded in part by the National Science Foundation (grant # MCB-1543922).

      AUTHOR CONTRIBUTIONS

      Ye Chu: Conceptualization; Data curation; Methodology; Writing-original draft. H. Thomas Stalker: Conceptualization; Data curation; Writing-review & editing. Kathleen Marasigan: Data curation; Writing-review & editing. Chandler M. Levinson: Data curation; Writing-review & editing. Dongying Gao: Data curation; Writing-review & editing. David J. Bertioli: Conceptualization; Writing-review & editing. Soraya C. M. Leal-Bertioli: Conceptualization; Writing-review & editing. C. Corley Holbrook: Conceptualization; Data curation; Writing-review & editing. Scott A. Jackson: Conceptualization; Writing-review & editing. Peggy Ozias-Akins: Conceptualization; Funding acquisition; Project administration; Supervision; Writing-review & editing.

      CONFLICT OF INTEREST

      The authors declare no conflict of interest.