Characterization and transferability of microsatellite markers of the cultivated peanut (Arachis hypogaea)

Background: the genus Arachis includes Arachis hypogaea (cultivated peanut) and wild species that are used in peanut breeding or as forage. Molecular markers have been employed in several studies of this genus, but microsatellite markers have only been used in few investigations. Microsatellites are very informative and are useful to assess genetic variability, analyze mating systems and in genetic mapping. The objectives of this study were to develop A. hypogaea microsatellite loci and to evaluate the transferability of these markers to other Arachis species.Results: Thirteen loci were isolated and characterized using 16 accessions of A. hypogaea. The level of variation found in A. hypogaea using microsatellites was higher than with other markers. Cross-transferability of the markers was also high. Sequencing of the fragments amplified using the primer pair AhII from 17 wild Arachis species showed that almost all wild species had similar repeated sequence to the one observed in A. hypogaea. Sequence data suggested that there is no correlation between taxonomic relationship of a wild species to A. hypogaea and the number of repeats found in its microsatellite loci.Conclusion: These results show that microsatellite primer pairs from A. hypogaea have multiple uses. A higher level of variation among A. hypogaea accessions can be detected using microsatellite markers in comparison to other markers, such as RFLP, RAPD and AFLP. The microsatellite primers of A. hypogaea showed a very high rate of transferability to other species of the genus. These primer pairs provide important tools to evaluate the genetic variability and to assess the mating system in Arachis species.

Genetic characterization of Brazilian annual Arachis species from sections Arachis and Heteranthae using RAPD markers

The genus Arachis is divided into nine taxonomic sections. Section Arachis is composed of annual and perennial species, while section Heteranthae has only annual species. The objective of this study was to investigate the genetic relationships among 15 Brazilian annual accessions from Arachis and Heteranthae using RAPD markers. Twenty-seven primers were tested, of which nine produced unique fingerprintings for all the accessions studied. A total of 88 polymorphic fragments were scored and the number of fragments per primer varied from 6 to 17 with a mean of 9.8. Two specific markers were identified for species with 2n = 18 chromosomes. The phenogram derived from the RAPD data corroborated the morphological classification. The bootstrap analysis divided the genotypes into two significant clusters. The first cluster contained all the section Arachis species, and the accessions within it were grouped based upon the presence or absence of the 'A' pair and the number of chromosomes. The second cluster grouped all accessions belonging to section Heteranthae.

A microsatellite-based, gene-rich linkage map for the AA genome of Arachis (Fabaceae)

Cultivated peanut (Arachis hypogaea) is an important crop, widely grown in tropical and subtropical regions of the world. It is highly susceptible to several biotic and abiotic stresses to which wild species are resistant. As a first step towards the introgression of these resistance genes into cultivated peanut, a linkage map based on microsatellite markers was constructed, using an F-2 population obtained from a cross between two diploid wild species with AA genome (A. duranensis and A. stenosperma). A total of 271 new microsatellite markers were developed in the present study from SSR-enriched genomic libraries, expressed sequence tags (ESTs), and by data-mining sequences available in GenBank. of these, 66 were polymorphic for cultivated peanut. The 271 new markers plus another 162 published for peanut were screened against both progenitors and 204 of these (47.1%) were polymorphic, with 170 codominant and 34 dominant markers. The 80 codominant markers segregating 1:2:1 (P < 0.05) were initially used to establish the linkage groups. Distorted and dominant markers were subsequently included in the map. The resulting linkage map consists of 11 linkage groups covering 1,230.89 cM of total map distance, with an average distance of 7.24 cM between markers. This is the first microsatellite-based map published for Arachis, and the first map based on sequences that are all currently publicly available. Because most markers used were derived from ESTs and genomic libraries made using methylation-sensitive restriction enzymes, about one-third of the mapped markers are genic. Linkage group ordering is being validated in other mapping populations, with the aim of constructing a transferable reference map for Arachis.

Novel polymorphic microsatellite markers in section Caulorrhizae (Arachis, Fabaceae)

This work reports the characterization of 11 polymorphic microsatellite loci in section Caulorrhizae. The primer pairs were designed from Arachis pintoi and showed full transferability to Arachis repens species. These new markers were used to evaluate the genetic diversity in germplasm (accessions and cultivars) of section Caulorrhizae. This new set of markers detected greater gene diversity than morphological and molecular markers such as AFLP (amplified fragment length polymorphism) and RAPD (rapid analysis of polymorphic DNA) previously used in this germplasm.

Genetic relationships among Arachis species based on AFLP

Amplified Fragment Length Polymorphism (AFLP) was used to establish the genetic relationships among 20 species from seven of the nine sections of genus Arachis. The level of polymorphism among nine accessions of the cultivated peanut, A. hypogaea L., was also evaluated. Three combinations of primers were used to amplify the AFLPs. The fragments were separated in 6% denaturing acrylamide gels. A total of 408 fragments were analyzed. An average of 135.3 fragments per primer combination were scored, and the largest number of fragments was 169 using primer combination Eco RI - ACC / Mse I - CTG, while the lowest was 108, with Eco RI - ACT / Mse I - CTT. In general, the genetic relationships established using AFLPs agreed with the classification established using morphology and crossability data. The results indicated that AFLPs are good markers for establishing the relationships among Arachis species. The polymorphism detected in A. hypogaea by this method was higher than the one found with other markers, like RAPDs and RFLPs. However, our data suggest that the polymorphism detected be using AFLP with only three primer combinations is still too low to be used for any kind of genetic study in this species.

Heterologous microsatellite primer pairs informative for the whole genus Arachis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic relationships among Arachis hypogaea L. (AABB) and diploid Arachis species with AA and BB genomes

The cultivated peanut (Arachis hypogaea L.) is an allotetraploid, with two types of genomes, classified as AA and BB, according to cytogenetic characters. Similar genomes to those of A. hypogaea are found in the wild diploid species of section Arachis, which is one of the nine Arachis sections. The wild species have resistances to pests and diseases that affect the cultivated peanut and are a potential source of genes to increase the resistance levels in peanut. The aim of this study was to analyze the genetic variability within AA and BB genome species and to evaluate how they are related to each other and to A. hypogaea, using RAPD markers. Eighty-seven polymorphic bands amplified by ten 10-mer primers were analyzed. The species were divided into two major groups, and the AA and the BB genome species were, in general, separated from each other. The results showed that high variation is available within species that have genomes similar to the AA and the BB genomes of A. hypogaea.

A linkage map for the B-genome of Arachis (Fabaceae) and its synteny to the A-genome

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bird attributes, plant characteristics, and seed dispersal of Pera glabrata (Schott, 1858), (Euphorbiaceae) in a disturbed cerrado area

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic markers between Biomphalaria glabrata snails susceptible and resistant to Schistosoma mansoni infection

The analysis of the genetic variability related to susceptibility to Schistosoma mansoni infection in the vector of the genus Biomphalaria is important in terms of a better understanding of the epidemiology of schistosomiasis itself, the possible pathological implications of this interaction in vertebrate hosts, and the formulation of new strategies and approaches for disease control. In the present study, the genetic variability of B. glabrata strains found to be resistant or susceptible to S. mansoni infection was investigated using DNA amplification by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The amplification products were analyzed on 8% polyacrylamide gel and stained with silver. We selected 10 primers, since they have previously been useful to detect polymorphism among B. glabrata and/or B. tenagophila. The results showed polymorphisms with 5 primers. Polymorphic bands observed only in the susceptible strain. The RAPD-PCR methodology represents an adequate approach for the analysis of genetic polymorphisms. The understanding of the genetic polymorphisms associated to resistance may contribute to the future identification of genomic sequences related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni and to the development of new strategies for the control of schistosomiasis.

Efeitos do período de matocompetição sobre a produtividade do amendoim (Arachis hipogaea L.)

Com o objetivo de estudar os efeitos de diferentes períodos de competição das plantas daninhas sobre alguns parâmetros produtivos da cultura do amendoim cv. Tatu-53, foi instalada e conduzida a presente pesquisa, em Jaboticabal, em solo Latossol Vermelho Escuro - fase arenosa. O delineamento experimental utilizado foi o de blocos casualizados, sendo os tratamentos divididos em dois grupos: no primeiro, a cultura foi mantida no mato desde a germinação até determinada fase de seu ciclo de desenvolvimento e, no segundo a cultura foi conservada livre da competição por períodos equ ivalentes ao primeiro grupo, após o qual o mato foi deixado crescer livremente. As extensões dos períodos estudados foram, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 e 100 dias. Nas condições em que foi desenvolvido o experimento, o amendoim mostrou-se relativamente tolerante à competição de maneira que um período de 10 dias livre das plantas daninhas no início de seu ciclo de desenvolvimento proporcionou -lhe condições ple nas de produtividade, comparada à te stemunha no limpo. Por outro lado, quando foi pe rmitido que o mato desenvolvesse desde o início do ciclo de cultura, o período acima do qual a competição alterou a produtividade de cultura foi igual ou superior a 50 dias.

Study of the genetic variability and similarity among and within Arachis villosulicarpa, A-pietrarellii and A-hypogaea through isoenzyme analysis

Arachis villosulicarpa is a perennial species cultivated for its soft and tasty seeds by indigenous inhabitants of the Mate Grosso State, Brazil. Besides A. hypogaea, this species is considered as the only species of Arachis which represents a valuable food source for human consumption. Due to the lack of knowledge concerning the genetic diversity of A. villosulicarpa, this study was conducted to evaluate the genetic variability of the accessions from the Germplasm Collection of CENARGEN/EMBRAPA (Brasilia, DF, Brazil) and Institute Agronomico (IAC, Campinas, SP, Brazil). In addition, the genetic similarity between A. villosulicarpa, the related wild species A. pietrarellii, and the cultivated peanut A. hypogaea cv. Tatu was evaluated. From the entire sample analyzed of A. villosulicarpa, the accession from Institute Agronomico showed the highest indices of diversity for both enzymatic systems analyzed, pointing this accession as a promising source of genetic variability that must be preserved in the Germplasm Bank. A high level of genetic similarity was observed between A. pietrarellii and A. villosulicarpa, supporting previous suggestions that A. pietrarellii could be the ancestral progenitor species of A. villosulicarpa or that both species originated from a common ancestor.

Botutatu: nova cultivar de amendoim (Arachis hypogaea L.)

Botutatu is a new released peanut cultivar, selected from the Brazilian cultivar Tatu by progeny testing. It belongs to Valencia type and has similar characteristics of cultivar Tatu, differing from the late by being 23.7% superior in pod yield.

RFLP analysis of genetic variation in species of section Arachis, genus Arachis (Leguminosae)

Four A-genome species of the genus Arachis ( A. cardenasii, A. correntina, A. duranensis, A. kempff-mercadoi), three B genomes species ( A. batizocoi, A. ipaensis and A. magna), the AABB allotetraploid A. hypogaea (cultivated peanut) and introgression lines resulting from a cross between A. hypogaea and A. cardenasii were analyzed by RFLP. The A genome species (cytologically characterized by the presence of a small chromosome pair 'A') were closely similar to each other and shared a large number of restriction fragments. In contrast, the B genome species differed more from one another and shared few fragments. The results of this study indicate that the absence of the small chromosome pair is not a good criterion for grouping species of section Arachis as B genome species, since their genome might be quite distinct from the B genome of A. hypogaea. The lowest genetic variation was detected within accessions of A. duranensis (17 accessions), followed by A. batizocoi (4 accessions) and A. cardenasii (9 plants of accession GKP 10017). The high level of genetic variation found in A. cardenasii might indicate that not all accessions of wild species of Arachis are autogamous, as reported for A. hypogaea.