The section Heteranthae of Arachis is endemic to Brazil, occurring mainly in the semi-arid northeastern region. The section is considered derived within the genus and includes only annual herbs. Most previous cytological evaluations were restricted to chromosome numbers and morphology. The present approach comprised karyomorphological evaluation in 10 accessions from five species of this section, including standard staining and fluorochrome banding [chromomycin A3 (CMA)/4 0 ,6-diamidino-2-phenylindole (DAPI)]. All accessions presented diploid chromosome numbers (2n = 20) with a prevalence of metacentric to submetacentric chromosome morphology. Arachis dardani, Arachis pusilla, and Arachis interrupta presented karyotypic formula 18m ? 4sm and satellite type 2, while Arachis sylvestris and Arachis giacomettii presented 16m ? 4sm and satellite type 10. Despite the conserved morphological features, higher diversity was detected in terms of size and number of GC-rich (CMA ?) heterochromatic blocks among the species; however, all of them were located in the pericentromeric regions. The species A. pusilla presented the highest number of GC-rich blocks, present in all chromosomes of the complement. Based on the data obtained and considering literature data, we suggest that A. dardani and A. interrupta occupy a basal position in the group due to their moderate asymmetry and satellite type. At least in A. pusilla, the constitutive heterochromatin seems to have suffered recent modifications of its constitution, in contrast to other species that present pericentromeric CMA ? blocks in all chromosomes. A. giacomettii and A. sylvestris are closely related to each other and also similar to the previously studied Arachis seridoensis, revealing two clear-cut subgroups within the section from the karyological point of view.

ABSTRACT. Somatic chromosome numbers were determined for 20 new germplasm accessions of Paspalum, belonging to 17 species collected in Brazil. Chromosome number is reported for the first time for P. reduncum (2n = 18), P. cinerascens (2n = 20), P. cordatum (2n = 20), P. filgueirasii (2n = 24), P. ammodes (2n = 36), P. bicilium (2n = 40), P. heterotrichon (2n = 40), and P. burmanii (2n = 48). New cytotypes were confirmed for two germplasm accessions of P. carinatum (2n = 30) and P. trachycoleon (2n = 36), one of P. clavuliferum (2n = 40) and one of P. lanciflorum (2n = 40), indicating variability in these species. The remaining chromosome numbers reported here confirm previous counts. The unexpected chromosome numbers 2n = 18, 24, 36, and 48 in Paspalum species, which are usually shown to be multiples of 10, suggest that much more collection and cytogenetic characterization are necessary to assess the whole chromosomal and genomic multiplicity present in the genus, which seems to be much more diverse than currently thought to be.

Arachis stenosperma is a wild relative of the groundnut, with a peculiar disjunct distribution in Central Brazil and along the Atlantic coast. Arachis species show one pair of satellited chromosomes (SAT) and some species have a distinct, smaller pair (A pair). The SAT chromosomes are classified according to 10 types. Previous literature information on A. stenosperma documents the presence of SAT type 3 only in the coastal populations, while type 5 was restricted to accessions from Central Brazil. This work sampled a broader area of geographic distribution, represented by an increased number of accessions, and provides further information on karyotypic characteristics. All 23 accessions analyzed present 2nϭ20. SAT type 5 was found in 10 accessions, irrespective to their area of occurrence. So, type 5 occurs also in the Atlantic coast. Type 3, so far exclusive to the Litoral, is not the most frequent type in the area. With the present data, the potential cytogenetic distinction between coastal and continental populations has vanished. The formula 18mϩ2sm clearly predominates, both in the Litoral and in Central Brazilian populations. Also irrespective to the area of origin, both idiogram positions A9/SAT10 and SAT9/A10 were identified. As the SAT of type 3 is considered more primitive than type 5, and the coastal area of distribution of A. stenosperma is secondary, it's future detection in continental populations is expected. In the meantime, a unique cytogenetic feature, the presence of SAT type 3 persists as an exclusive attribute of the populations of the secondary area of occurrence.

ABSTRACT. Arachis kuhlmannii occurs in Mato Grosso and Mato Grosso do Sul States, Brazil. Its area of occurrence partially overlaps with that of other species in the Arachis section. Because of their morphological similarities, these species are often mistaken one for another. This study aimed the correct classification of available accessions as Arachis kuhlmannii, or other species, and the characterization of similarities among accessions and Arachis hypogaea by morphological, cytogenetic, and molecular marker analyses. Thirtyeight accessions were used. Principal component analysis was used for morphological characterization, root tips for mitotic metaphase analysis, and RAPD markers for molecular characterization. Cluster analysis discriminated accessions with the A genome from the B genome. Cluster analysis based on molecular markers discriminated natural populations in a manner that correlated with geographical areas of the collection. Arachis cardenasii and A. hypogaea were isolated from other A-genome accessions. Cytogenetic analyses confirmed the existence of diagnostic characteristics that distinguish species with the A genome from those with the B genome. Results suggest the need for a taxonomic review of some species in the Arachis section, as we could not discriminate as distinct species all of the accessions identified as A. kuhlmannii, A. helodes, and A. simpsonii by using morphological, molecular, and cytogenetic markers.