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Background and Aims The genus Arachis contains 80 described species. Section Arachis is of particular interest because it includes cultivated peanut, an allotetraploid, and closely related wild species, most of which are diploids. This study aimed to analyse the genetic relationships of multiple accessions of section Arachis species using two complementary methods. Microsatellites allowed the analysis of inter- and intraspecific variability. Intron sequences from single-copy genes allowed phylogenetic analysis including the separation of the allotetraploid genome components. Methods Intron sequences and microsatellite markers were used to reconstruct phylogenetic relationships in section Arachis through maximum parsimony and genetic distance analyses. Key Results Although high intraspecific variability was evident, there was good support for most species. However, some problems were revealed, notably a probable polyphyletic origin for A. kuhlmannii. The validity of the genome groups was well supported. The F, K and D genomes grouped close to the A genome group. The 2n = 18 species grouped closer to the B genome group. The phylogenetic tree based on the intron data strongly indicated that A. duranensis and A. ipaënsis are the ancestors of A. hypogaea and A. monticola. Intron nucleotide substitutions allowed the ages of divergences of the main genome groups to be estimated at a relatively recent 2·3–2·9 million years ago. This age and the number of species described indicate a much higher speciation rate for section Arachis than for legumes in general. Conclusions The analyses revealed relationships between the species and genome groups and showed a generally high level of intraspecific genetic diversity. The improved knowledge of species relationships should facilitate the utilization of wild species for peanut improvement. The estimates of speciation rates in section Arachis are high, but not unprecedented. We suggest these high rates may be linked to the peculiar reproductive biology of Arachis. [ABSTRACT FROM AUTHOR]

• Background and Aims Hylocereus and Selenicereus are native to tropical and sub-tropical America. Based on its taxonomic status and crossability relations it was postulated that H. megalanthus (syn. S. megalanthus) is an allotetraploid (2n = 4x = 44) derived from natural hybridization between two closely related diploid taxa. The present work aimed at elucidating the genetic relationships between species of the two genera.• Methods Crosses were performed and the putative hybrids were analysed by chromosome counts and morphological traits. The ploidy level of hybrids was confirmed by fluorescent in situ hybridization (FISH) of rDNA sites. Genomic in situ hybridization (GISH) was used in an attempt to identify the putative diploid genome donors of H. megalanthus and an artificial interploid hybrid.• Key Results Reciprocal crosses among four diploid Hylocereus species (H. costaricensis, H. monacanthus (syn. H. polyrhizus), H. undatus and Hylocereus sp.) yielded viable diploid hybrids, with regular chromosome pairing. Reciprocal crosses between these Hylocereus spp. and H. megalanthus yielded viable triploid, pentaploid, hexaploid and aneuploid hybrids. Morphological and phenological traits confirm the hybrid origin. In situ detection of rDNA sites was in accord with the ploidy status of the species and hybrid studied. GISH results indicated that overall sequence composition of H. megalanthus is similar to that of H. ocamponis and S. grandiflorus. High sequence similarity was also found between the parental genomes of H. monacanthus and H. megalanthus in one triploid hybrid.• Conclusions The ease of obtaining partially fertile F1 hybrids and the relative sequence similarity (in GISH study) suggest close genetic relationships among the taxa analysed. [ABSTRACT FROM AUTHOR]

RAPD markers were used to study variation among 20 taxa in the genus Orobanche: O. alba, O. amethystea, O. arenaria, O. ballotae, O. cernua, O. clausonis, O. cumana, O. crenata, O. densiflora, O. foetida, O. foetida var. broteri, O. gracilis, O. haenseleri, O. hederae, O. latisquama, O. mutelii, O. nana, O. ramosa, O. rapum‐genistae and O. santolinae. A total of 202 amplification products generated with five arbitrary RAPD primers was obtained and species‐specific markers were identified. The estimated Jaccard’s differences between the species varied between 0 and 0·864. The pattern of interspecific variation obtained is in general agreement with previous taxonomic studies based on morphology, and the partition into two different sections (Trionychon and Orobanche) is generally clear. However, the position in the dendrogram of O. clausonis did not fit this classification since it clustered with members of section Trionychon. Within this section, O. arenaria was relatively isolated from the other members of the section: O. mutelii, O. nana and O. ramosa. Within section Orobanche, all O. ramosa populations showed a similar amplification pattern, whereas differences among O. crenata populations growing on different hosts were found. Orobanche foetida and O. densiflora clustered together, supporting the morphological and cytological similarities and the host preferences of these species. [ABSTRACT FROM AUTHOR]

Nineteen accessions ofVigna luteola,five ofV. marinassp.oblonga, and two ofV. marinassp.marinawere analysed using variation of isozymes and RAPD markers to obtain better insight into genetic relationships within and between these taxonomic entities. Thirteen putative isozyme loci were scored, seven of which were polymorphic. Both species showed very low genetic diversity indices and most of the variation was detected among populations. Pairwise Nei's genetic distances based on allozyme frequencies were also very low and the accessions ofV. marinassp.marinawere the least related to the others. RAPD analysis was more discriminating and 66 bands out of a total of 85 were polymorphic. Based on the presence or absence of bands, Jaccard's similarity index was calculated. Similarity ranged from 0.476 to 0.98. Matrices derived from both isozyme and RAPD data were used to construct UPGMA dendrograms. In the tree obtained from Nei's genetic distance, based on allozyme frequencies, accessions belonging toV. marinassp.oblongawere mixed withV. luteolaaccessions; on the other hand, the twoV. marinassp.marinaclustered separately, with oneV. luteola.The dendrogram derived from RAPD data showed three main groups corresponding to the three taxa analysed. Moreover, according to these data,V. marinassp.oblongais more closely related toV. luteolathan toV. marinassp.marina.Copyright 1997 Annals of Botany Company [ABSTRACT FROM AUTHOR]