Sections Erectoides Research Articles

Taxonomía del género Arachis (Leguminosae)

Taxonomía del género Arachis (Leguminosae)

Genetic relationships of Arachis (Fabaceae) accessions based on microsatellite markers

The genus Arachis is endemic to South America and contains 83 described species assembled into nine taxonomical sections. The section Arachis is of particular interest because it includes the cultivated peanut (A. hypogaea) and its closely related wild species. In this study, we used 26 microsatellite markers to analyze the genetic variability and relationships of some recently collected germplasm accessions of species in the Arachis section, with emphasis on the B genome species. The knowledge of the genetic relationships among species and accessions is necessary for a more efficient management of germplasm collections and use of wild species for crop improvement. This is especially important for the B genome species, as only one accession of A. ipaënsis, the B genome donor to the allotetraploid A. hypogaea (AABB), is available in germplasm collections worldwide. The results shed more light on the genetic relationships between accessions of A. ipaënsis, A. gregoryi, A. magna, A. valida and A. williamsii, what expands the number of accessions for incorporation of useful genes from the species associated with the peanut B genome. The analyses also showed a generally high level of intraspecific genetic variability, but usually grouped the accessions according to their genome types and species. However, accessions of some species did not group as expected, and these results suggest the need of further taxonomic revision of a few taxa, especially some accessions of A. gregoryi, A. magna and A. kuhlmannii and the circumscriptions of sections Erectoides and Procumbentes.

Genomic relationships of the polyploid rhizoma peanut (Arachis glabrata Benth.) inferred by genomic in situ hybridization (GISH)

The rhizoma peanut (Arachis glabrata Benth., section Rhizomatosae) is a tetraploid perennial legume. Although several A. glabrata cultivars have been developed as forage and ornamental turf, the origin and genomic constitution of this species are still unknown. In this study, we evaluated the affinity between the genomes of A. glabrata and the probable diploid donors of the sections Rhizomatosae, Arachis, Erectoides and Procumbentes by genomic in situ hybridization (GISH). Single GISH analyses detected that species of the sections Erectoides (E2 subgenome) and Procumbentes (E3 subgenome) were the diploid species with the highest degree of genomic affinity with A. glabrata. Based on single GISH experiments and DNA sequence similarity, three species -A. duranensis, A. paraguariensis subsp. capibarensis, and A. rigonii-, which showed the most uniform and brightest hybridization patterns and lowest genetic distance, were selected as probes for double GISH experiments. Double GISH experiments showed that A. glabrata is constituted by four identical or very similar chromosome complements. In these assays, A. paraguariensis subsp. capibarensis showed the highest brightness onto A. glabrata chromosomes. Thus, our results support the autopolyploid origin of A. glabrata and show that the species with E2 subgenome are the most probable ancestors of this polyploid legume forage.

Cytogenetic evidences on the evolutionary relationships between the tetraploids of the section Rhizomatosae and related diploid species (Arachis, Leguminosae).

Rhizomatosae is a taxonomic section of the South American genus Arachis, whose diagnostic character is the presence of rhizomes in all its species. This section is of particular evolutionary interest because it has three polyploid (A. pseudovillosa, A. nitida and A. glabrata, 2n = 4x = 40) and only one diploid (A. burkartii, 2n = 2x = 20) species. The phylogenetic relationships of these species as well as the polyploidy nature and the origin of the tetraploids are still controversial. The present study provides an exhaustive analysis of the karyotypes of all rhizomatous species and six closely related diploid species of the sections Erectoides and Procumbentes by cytogenetic mapping of DAPI/CMA heterochromatin bands and 5S and 18-26S rDNA loci. Chromosome banding showed variation in the DAPI heterochromatin distribution pattern, which, together with the number and distribution of rDNA loci, allowed the characterization of all species studied here. The bulk of chromosomal markers suggest that the three rhizomatous tetraploid species constitute a natural group and may have at least one common diploid ancestor. The cytogenetic data of the diploid species analyzed evidenced that the only rhizomatous diploid species-A. burkartii-has a karyotype pattern different from those of the rhizomatous tetraploids, showing that it is not likely the genome donor of the tetraploids and the non-monophyletic nature of the section Rhizomatosae. Thus, the tetraploid species should be excluded from the R genome, which should remain exclusively for A. burkartii. Instead, the karyotype features of these tetraploids are compatible with those of different species of the sections Erectoides and Procumbentes (E genome species), suggesting the hypothesis of multiple origins of these tetraploids. In addition, the polyploid nature and the group of diploid species closer to the tetraploids are discussed.

Genomic characterisation of Arachis porphyrocalyx (Valls & C.E. Simpson, 2005) (Leguminosae): multiple origin of Arachis species with x = 9.

The genus Arachis Linnaeus, 1753 comprises four species with x = 9, three belong to the section Arachis: Arachis praecox (Krapov. W.C. Greg. & Valls, 1994), Arachis palustris (Krapov. W.C. Greg. & Valls, 1994) and Arachis decora (Krapov. W.C. Greg. & Valls, 1994) and only one belongs to the section Erectoides: Arachis porphyrocalyx (Valls & C.E. Simpson, 2005). Recently, the x = 9 species of section Arachis have been assigned to G genome, the latest described so far. The genomic relationship of Arachis porphyrocalyx with these species is controversial. In the present work, we carried out a karyotypic characterisation of Arachis porphyrocalyx to evaluate its genomic structure and analyse the origin of all x = 9 Arachis species. Arachis porphyrocalyx showed a karyotype formula of 14m+4st, one pair of A chromosomes, satellited chromosomes type 8, one pair of 45S rDNA sites in the SAT chromosomes, one pair of 5S rDNA sites and pericentromeric C-DAPI+ bands in all chromosomes. Karyotype structure indicates that Arachis porphyrocalyx does not share the same genome type with the other three x = 9 species and neither with the remaining Erectoides species. Taking into account the geographic distribution, morphological and cytogenetic features, the origin of species with x = 9 of the genus Arachis cannot be unique; instead, they originated at least twice in the evolutionary history of the genus.

Phylogenetic relationships in genus Arachis based on ITS and 5.8S rDNA sequences

BackgroundThe genus Arachis comprises 80 species and it is subdivided into nine taxonomic sections (Arachis, Caulorrhizae, Erectoides, Extranervosae, Heteranthae, Procumbentes, Rhizomatosae, Trierectoides, and Triseminatae). This genus is naturally confined to South America and most of its species are native to Brazil. In order to provide a better understanding of the evolution of the genus, we reconstructed the phylogeny of 45 species using the variation observed on nucleotide sequences in internal transcribed spacer regions (ITS1 and ITS2) and 5.8 S of nuclear ribosomal DNA.ResultsIntraspecific variation was detected, but in general it was not enough to place accessions of the same species in different clades. Our data support the view that Arachis is a monophyletic group and suggested Heteranthae as the most primitive section of genus Arachis. The results confirmed the circumscriptions of some sections (Caulorrhizae, Extranervosae), but raised questions about others. Sections Erectoides, Trierectoides and Procumbentes were not well defined, while sections Arachis and Rhizomatosae seem to include species that could be moved to different sections. The division of section Arachis into A and B genome species was also observed in the phylogenetic tree and these two groups of species may not have a monophyletic origin. The 2n = 2x = 18 species of section Arachis (A. praecox, A. palustris and A. decora) were all placed in the same clade, indicating they are closely related to each other, and their genomes are more related to B genome than to the A genome. Data also allowed insights on the origin of tetraploid A. glabrata, suggesting rhizome appeared twice within the genus and raising questions about the placement of that species in section Rhizomatosae.ConclusionThe main clades established in this study in general agreed with many other studies that have used other types of evidences and sets of species, being some of them included in our study and some not. Thus, the relationships established can be a useful framework for future systematic reviews of genus Arachis and for the selection of species to pre-breeding programs.

Species, genomes, and section relationships in the genus Arachis (Fabaceae): a molecular phylogeny

The economically important genus Arachis (Fabaceae) comprises 80 species restricted to South America. One monograph on the genus divided it into nine sections and included an intuitive assessment of evolutionary relationships. There is no comprehensive phylogenetic study of the genus. To test the current systematic treatment of the genus, we reconstructed a phylogeny for Arachis using nuclear ITS and plastid trnT–trnF sequences from 46 species representing all nine sections. ITS cloning of the allotetraploid species of section Arachis indicated the presence of A and B genome alleles and chimeric sequences. Our study revealed that species from section Extranervosae were the first emerging lineage in the genus, followed by sections Triseminatae and Caulorrhizae, and two terminal major lineages, which we refer to as erectoides and arachis. The lineage erectoides comprises members of sections Erectoides, Heteranthae, Procumbentes, Rhizomatosae, and Trierectoides. Species in the arachis lineage form two major clades, arachis I (B and D genomes species and the aneuploids) and arachis II (A genome species). Our results substantiated the sectional treatment of Caulorrhizae, Extranervosae, and Triseminatae, but demonstrated that sections Erectoides, Procumbentes, and Trierectoides are not monophyletic. A detailed study of the genus Arachis with denser taxon sampling, additional genomic regions, plus information from morphology and cytogenetics is needed for comprehensive assessment of its systematics.

The role of BAP in somatic embryogenesis induction from seed explants of Arachis species from Sections Erectoides and Procumbentes

Somatic embryogenesis was induced from seed explants of Arachis archeri, A. porphyrocalix (Section Erectoides) and A. appressipila (Section Procumbentes) in response to 6-benzylaminopurine (BAP). Embryo axes first developed into single shoots in response to 4.4 μM BAP. Friable embryogenic calluses were produced from the hypocotyl region of these explants in response to different BAP concentrations. Embryonic leaflets also gave rise to friable calluses, but somatic embryos were only observed in explants of A. archeri and A. appressipila. Histological analyses revealed the presence of heart-shaped, torpedo and cotyledonary stages embryos, both as isolated and fused structures. A low frequency of embryo-to-plant conversion was achieved by inducing shoot development on medium solidified with 0.5% phytagel and supplemented with 1.5% or 3% sucrose. Rooting was induced on MS supplemented with indole-3-acetic acid (IAA).

In vitro regeneration and conservation of wild species of Arachis

SummaryWild species of Arachis are restricted to South America and generally occur in regions under intensive environmental disturbance. Both in situ and ex situ conservation strategies are required in order to maintain the availability of these genotypes. This work developed in vitro regeneration systems from seed explants of 17 wild species of Arachis from six Sections (Heteranthae, Caulorrhizae, Triseminatae, Erectoides, Procumbentes and Arachis). After seed disinfection, embryonic axes, leaflets and cotyledons were excised aseptically and cultured on Murashige and Skoog (MS) medium supplemented with 8.8 µM, 22 µM or 110 µM 6-benzylaminopurine (BAP). Cultures were maintained in a growth chamber at 28° ± 2°C with a 16 h photoperiod. Regeneration patterns from seed explants were similar among species from all Sections. Embryonic axes produced plants through meristematic amplification or multiple shoot formation, while cotyledons and embryonic leaflets produced shoots at significantly lower frequencies through direct and indirect organogenesis, respectively. Shoots obtained from all explants were transferred to MS medium without growth regulators to induce root formation.

Número cromosómico y morfología del cromosoma satelitado en once espécies de <i>Arachis</i> (Leguminosae)

Se determinó el número cromosómico de once especies recientemente descriptas del género Arachís, pertenecientes a cinco secciones taxonómicas. En la sección Arachís, A. Gregoryí y A. Krapovíckasíí presentan 2n520 cromosomas sin el par “A”, mientras A. línearífolía y A. Schíníníí presentan 2n520, incluyendo el par “A”, típico del genomio A de A. hypogaea. Arachís Schíníníí presenta características citológicas (presencia del par “A”) y morfológicas distintas de A. Hoehneí, bajo la cual estuvo incluida. Arachís submargínata (sección Extranervosae), A. Pflugeae y A. Hasslerí (sección Procumbentes), y A. serídoénsís y A. ínterrupta (sección Heteranthae) también presentan 2n520. Una especie de la sección Rhízomatosae, A. nítída, es tetraploide, con 2n540, pero morfológicamente distinta de las demás especies tetraploides de la sección. En la sección Erectoídes, la nueva especie A. porphyrocalyx presenta 2n518. Este es el primer recuento de 18 cromosomas en especies de Arachís que no pertenecen a la sección Arachís y su origen no está asociado al origen de los 18 cromosomas de las tres especies de la sección Arachís.

Chromosomal characterization of germplasm of wild species ofArachisL. belonging to sections Trierectoides, Erectoides and Procumbentes

Abstract Karyotypes of five species of genus Arachis belonging to three sections are described for the first time. Section Trierectoides: A. tuberosa Bong. ex Benth. (2n=2x=20m), section Erectoides: A. douradiana Krapov. and W.C. Gregory (2n=2x=18m+2sm), section Procumbentes: A. subcoriacea Krapov. and W.C. Gregory (2n=2x=18m+2sm), A. appressipila Krapov. and W.C. Gregory (2.=2x=14m+6sm) and A. Vallsii Krapov. and W.C. Gregory (2n=2x=18m+2sm). Satellited chromosomes are analysed for all species. “A” chromosomes were not found in none of them. Chromosome and exomorphology data suggest that A. Vallsii merit to be exclude from section Procumbentes.

Hybridization barriers among the species of arachis L., namely of the sections arachis (including the groundnut) and erectoides

Some members of section Erectoides have been found resistant to early leaf spot disease, a serious constraint to groundnut productivity. These accessions do not cross with cultivated species. Crossing between one such diploid species, A. paraguariensis (ICGs 8130 and 8973) of section Erectoides, and the diploids, A. batizocoi and A. duranensis, and the tetraploid A. hypogaea (groundnut) of section Arachis has helped understand barriers to hybridization between sections. These crosses result in the development of normal pegs and pods, but with of ovule and embryo development restricted or non-existent. Such restricted growth and embryo abortion is found to be due to cessation of early endosperm development in A. duranensis (2x) times A. paraguariensis (2x), the non-development of endosperm beyond the coenocytic stage in A. batizocoi (2x) times A. paraguariensis (2x), and the overgrowth of nucellar tissue into the embryo sac in case of A. hypogaea (4x) times A. paraguariensis (2x). The weak cross-compatibility between the species of two sections suggest relatively closer phylogenetic relationship between them, than with the other incompatible sections of the genus Arachis.

Seed storage protein variation in Arachis species

Seventy-two accessions, representing 22 species from sections Arachis, Erectoides, Extranervosae, and Triseminalae of the genus Arachis, were screened for seed storage protein polymorphism. Variation was detected between sections, between genome types, between species, and in some cases between different accessions of the same species or different seeds of the same accession. Arachis duranensis and one accession of A. cardenasii were found to have identical protein patterns. The greatest dissimilarity was found between species of the section Extranervosae and species of the section Triseminalae. Those of section Erectoides showed much similarity with some species of section Arachis. Protein polymorphism was shown to distinguish the two subspecies of A. hypogaea (fastigiata and hypogaea) in 27 of 28 cases. The seed protein profile of A. monticola was a combination of seed protein profiles from the two A. hypogaea subspecies. The relatedness between the various species was calculated and those that had the greatest similarity with A. hypogaea were A. spegazzinii and A. batizocoi.

Identification of Peanut Stripe Virus Resistance in Wild Arachis Germplasm1,,2

Abstract Fifty four wild Arachis germplasm accessions were evaluated for resistance to peanut stripe virus (PStV) by mechanical, aphid, and graft inoculations. Three weeks after inoculation, inoculated and subsequently produced leaflets of each entry were tested for PStV presence by enzyme-linked immunosorbent assay (ELISA). Peanut accessions in the section Arachis, A. cardenasii [ICG 11558 (PI 475998)] could not be infected by mechanical, aphid, and graft transmission tests, while A. chacoense [ICG 4983 (PI 276235)], A. cardenasii [ICG 11562 (PI 476012) and ICG 12168 (PI 476013)] and accessions of section Erectoides, A. sp. [ICG 11560 (PI 476004) and ICG 8215 (PI 468170)] and A. paraguariensis [ICG 8973 (PI 468176)], were infected by grafting, but not by aphid and mechanical inoculations.

Cytogenetical studies in the diploid interspecific hybrids of section Erectoides in the genus Arachis.

Three diploid interspecific hybrids and two reciprocal hybrids were produced between the species of section Erectoides. The cytological analysis in two hybrids and their reciprocal crosses shows 10 bivalents at diakinesis and metaphase-I in most of the PMCs and 2-4 univalents are seen in about 10 to 15 percent of cells. Further the hybrid between A. sp. 9990×A. sp. 10002 reveals a ring of four chromosomes in approximately 18 percent of the PMCs. In the hybrid A. regonii×A. sp 9990 and its reciprocal, chromatin bridge is seen in 8.4 percent of the cells at anaphase-II, thus providing cytological evidences for the possible role of structural changes in speciation of the section Erectoides.

Chromosome morphology in species of the sections, Erectoides and Extranervosae of the genus Arachis L.

Chromosome morphology at pachytene was studied in two species; A. sp. (GKP 9990, Section. Erectoides) and A. villosulicarpa (Section. Extranervosae) and compared with the other sectional species. The genus Arachis appeared to be based on a basic karyotype of six differentiated chromosomes, three specialised chromosomes and one nucleolus organizer. The karyotypes of species belonging to sections Erectoides, Triseminale and Extranervosae appeared to be more primitive than sections Arachis and Rhizomatosae. The section Arachis appeared to be a natural group of cross-compatible species having the characteristic A chromosome with the exception of A. batizocoi. The pachytene chromosome morphology did not indicate a highly marked chromosomal differentiation between the A' and ‘B’ genomes assumed to be present in the cultivated groundnut. Specific differences have been thought to be brought about in the genus Arachis through minor structural repatterning and major genetic differentiation.

Hybrids in the Genus Arachis Between Sections Erectoides and Arachis1

The objective of this study was to determine whether diploid members of section Arachis could potentially be used as bridges between section Erectoides Krap. et. Greg. nom. nud. and A. hypogaea. Two diploid (2n = 20) taxa of section Erectoides and their F1 and F2C1 hybrids were evaluated. The female parent, A. rigonii Krap. et Greg. (PI 262142, collection no. GKP 10034), and male parent, A. sp. (PI 262278, collection no. GKP 9841) had perfect bivalent formation, but the F1 did not produce enough flowers to cytologically examine. The F2C1 averaged 2.76 univalents, 18.48 bivalents, 0.04 trivalents, and 0.04 quadrivalents per pollen mother cell and pairing of chromosomes between the two section Erectoides species is believed to be minimal. Hybrids between the F2C1 and the diploid section Arachis species A. stenosperma Greg. et Greg, nom. nud. (PI 338280, collection no. HLK 410) and A. duranensis Krap. et Greg. nom. nud. (PI 219823, collection no. K 7988) were studied. Multivalents were observed at a low frequency. Members of sections Erectoides and Arachis may have a common genome.The results indicate that gene transfer from section Erectoides species into the cultivated peanut seems possible by using diploid members of section Arachis as bridge species. Early metaphase I microsporocytes with an unreduced chromosome number were observed in three hybrids. Two fruits were recovered from intersectional colchicine‐treated hybrids, but the seeds were inviable. Future success in restoring fertility may depend on propagating large numbers of colchicine‐treated cuttings.

Resistance of Wild Species of Arachis to the Twospotted Spider Mite, Tetranychus Urticae1,2,3

Abstract Wild species of Arachis representing all seven sections of the genus were screened in the greenhouse for resistance to the twospotted spider mite, Tetranychus urticae Koch. Most species of the section RHIZOMATOSAE were found to be highly resistant to the mite. Plant introductions 338296, 338317, 262840, 262827 and several other members of the section RHIZOMATOSAE were virtually mite free throughout the tests. PI 276203 from section EXTRANERVOSAE, PI 262142 from section ERECTOIDES and PI 331194 from section ARACHIS also had relatively low damage ratings in this study. Section Arachis is the only section with resistance to the mite that will cross readily with cultivated peanuts, Arachis hypogaea L. Thus the utilization of germplasm resistant to the mite from the wild species will require complicated and difficult breeding procedures.

Sources and Nature of Resistance to Cercospora Arachidicola Hori and Cercosporidium Personatum (Beck & Curtis) Deighton in Arachis Species1

Abstract Various subspecies, botanical varieties and cultivars of peanuts (Arachis hypogaea L.) from widely separated areas of South America and Africa were evaluated for resistance to C. personatum and C. arachidicola. All cultivated peanuts tested were highly susceptible to both fungi except one collection from Peru, which showed a high degree of tolerance to defoliation. Sources of resistance were found in the wild Arachis species. Several immune and many highly resistant collections of Arachis were found in the sections Erectoides, Rhizomatosae, and Extranervosae. In section Axonomorphae, A. chacoense (10602 GKP) was highly resistant to C. arachidicola but susceptible to C. personatum, and C. cardenasii (10017 GKP) was susceptible to C. arachidicola but immune to C. personatum. Both Arachis species are cross-compatible with A. hypogaea. Host response in terms of pathogen penetration was classified into: immune, moderately and highly susceptible; and the reactions after penetration were: highly resistant, moderately and highly susceptible. On highly susceptible peanuts, the germ-tubes showed directed growth toward open stomata through which these fungi penetrate. On moderately susceptible peanuts a few germ-tubes grew toward the stomata, and on the immune entries no directed growth of the germ-tubes was observed. Resistance after penetration was associated with the formation of a barrier in advance of and around the infection site in the form of cell wall swelling and thickening, and the deposition of pectic substances on the cell walls and in intercellular spaces.