Integrating genetic maps in bambara groundnut [Vigna subterranea (L) Verdc.] and their syntenic relationships among closely related legumes

Background Bambara groundnut [Vigna subterranea (L) Verdc.] is an indigenous legume crop grown mainly in subsistence and small-scale agriculture in sub-Saharan Africa for its nutritious seeds and its tolerance to drought and poor soils. Given that the lack of ex ante sequence is often a bottleneck in marker-assisted crop breeding for minor and underutilised crops, we demonstrate the use of limited genetic information and resources developed within species, but linked to the well characterised common bean (Phaseolus vulgaris) genome sequence and the partially annotated closely related species; adzuki bean (Vigna angularis) and mung bean (Vigna radiata). From these comparisons we identify conserved synteny blocks corresponding to the Linkage Groups (LGs) in bambara groundnut genetic maps and evaluate the potential to identify genes in conserved syntenic locations in a sequenced genome that underlie a QTL position in the underutilised crop genome. Results Two individual intraspecific linkage maps consisting of DArTseq markers were constructed in two bambara groundnut (2n = 2x = 22) segregating populations: 1) The genetic map of Population IA was derived from F2 lines (n = 263; IITA686 x Ankpa4) and covered 1,395.2 cM across 11 linkage groups; 2) The genetic map of Population TD was derived from F3 lines (n = 71; Tiga Nicuru x DipC) and covered 1,376.7 cM across 11 linkage groups. A total of 96 DArTseq markers from an initial pool of 142 pre-selected common markers were used. These were not only polymorphic in both populations but also each marker could be located using the unique sequence tag (at selected stringency) onto the common bean, adzuki bean and mung bean genomes, thus allowing the sequenced genomes to be used as an initial ‘pseudo’ physical map for bambara groundnut. A good correspondence was observed at the macro synteny level, particularly to the common bean genome. A test using the QTL location of an agronomic trait in one of the bambara groundnut maps allowed the corresponding flanking positions to be identified in common bean, mung bean and adzuki bean, demonstrating the possibility of identifying potential candidate genes underlying traits of interest through the conserved syntenic physical location of QTL in the well annotated genomes of closely related species. Conclusions The approach of adding pre-selected common markers in both populations before genetic map construction has provided a translational framework for potential identification of candidate genes underlying a QTL of trait of interest in bambara groundnut by linking the positions of known genetic effects within the underutilised species to the physical maps of other well-annotated legume species, without the need for an existing whole genome sequence of the study species. Identifying the conserved synteny between underutilised species without complete genome sequences and the genomes of major crops and model species with genetic and trait data is an important step in the translation of resources and information from major crop and model species into the minor crop species. Such minor crops will be required to play an important role in future agriculture under the effects of climate change

Chromosome studies in Brazilian species of Campomanesia Ruiz & Pavon and Psidium L. (Myrtaceae Juss.)

In this work, we carried out chromosome counts of four species of Campomanesia (C. adamantium, C. guaviroba, C. phaea and C pubescens) and four of Psidum (P. acutangulum, P. cattleyanum, P. cinereum and P. guajava) from different populations. In Campomanesia, 2n=22 was found in all of the species analyzed, and no polyploidy was seen, For Psidium, only P. guajava had 2n=22 and another three species had 2n=44. No abnormalities in meiosis were observed. High levels of pollen stainability (> 80%) was seen in all species. About 50% of Myrtinae species were polyploid, indicating the importance of polyploidy in the evolution of this group.59171

Cytogenetics of twelve species of Malpighiaceae A. Juss. from Southeastern Brazil

The family Malpighiaceae shows a great chromosomal number diversity, with polyploidy and disploidy between and within species. Cytological studies have played an important role in the taxonomy of Malpighiaceae. In the present work we studied twelve species and present the chromosome numbers and for seven of them karyomorphological characters and chromosomal ideograms. The chromosomes are predominantly small and metacentric. No meiotic abnormalities were found, and they presented a high viable pollen index. We analyzed the relationship between the taxonomic distribution of taxa and the distribution of chromosomal numbers in Malpighiaceae species. The sub-family Malpighioideae presents chromosome numbers based on x = 5 and he subfamily Byrsonimoideae presents numbers based on x = 6. The basic number x = 5 for Malpighiaceae is a new proposal, supported by some counts for the genera Banisteriopsis, Heteropterys, Peixotoa and Tetrapterys.55324125

A triploid cytotype of Echinodorus tennellus

We describe the existence of two Echinodorus tennellus cytotypes, with diploid populations, of 2n = 22 chromosomes, and triploid ones, with 2n = 33. Meiotic studies showed abnormalities and 50% pollen stainability in plants of triploid populations, but 100% pollen stainability in a diploid population. Data from C-banding and CMA/DAPI (Chromomycin A(3)/4,6-diamidino-2-phenylindole) fluorescent banding showed the diploid population has one CMA+/DAPI+ band, equivalent to the heterochromatic region of C-banding, while a triploid population has two CMA+/DAPI+ heterochromatic regions, suggesting an autopoliploid origin for the triploid cytotype. The autotriploid origin was also supported by the trivalent pairing of chromosomes and the presence of three sets of each chromosome in mitotic metaphase. Diploid and triploid cytotypes were easily maintained through vegetative propagation of this stoloniferous species. (C) 2004 Elsevier B.V. All rights reserved.79432533

Longitudinal differentiation in chromosomes of some Sesbania Scop. species (Fabaceae)

Three different techniques were applied to analyze the patterns of longitudinal chromosome differentiation in five Sesbania species (S. exasperata, S. punicea, S. sesban, S. tetraptera, and two different geographical populations of S. virgata). For all the species investigated, the prophase chromosome condensation was always proximal. After staining with the fluorochromes chromomycin A(3) and DAPI, each karyotype revealed two or four CMA(+)/DAPI(-) heterochromatic blocks, apparently corresponding to the nucleolus organizing regions. However, in S. virgata two or four CMA(+) bands were observed, depending on the population studied. No DAPI(+) bands were observed. C-banding showed the most diversified patterns, being a more useful technique to distinguish karyorypes of Sesbania species. The largest amount of heterochromatin was observed in S. virgata (subgenus Daubentonia) whereas the smallest was found in S. sesban (subgenus Sesbania).52416719710

Chromosomal studies of species of Rubiaceae (A. L. de Jussieu) from the Brazilian cerrado

The chromosomes of 14 species belonging to two subfamilies of the family Rubiaceae collected in the Brazilian cerrado were studied. In the subfamily Ixoroideae, five species (Alibertia concolor, A. edulis, A. sessilis, Genipa americana and Tocoyena formosa) had a chromosome number of 2n = 22 and one (Amaioua intermedia) showed polyploidy, with 2n = 66. All of the chromosome numbers were multiples of the more common basic number for this family (x = 11). In the subfamily Rubioideae, variations in the number of chromosomes were observed among tribes and genera, with 2n = 20 in the tribe Coccocypseleae (Coccocypselum lanceolatum), 2n = 28 in Spermacoceae (Borreria latifolia, B. verticillata and Richardia brasiliensis) and n = 11 in Coussareeae (Coussarea hydrangeifolia). In the tribe Psychotrieae, the variations included n = 11 (Palicourea rigida), 2n = 22 (Psychotria hoffmannseggiana) and 2n = 32 (Psychotria deflexa). The ideograms elaborated for 1 species were symmetrical (TF% varied from 47.45 to 38.01). The size of the chromosomes ranged from 1.26 to 7.33 mum and most were metacentric. The results show that chromosome size and morphology were insufficient to differentiate among groups within the Rubiaceae.57325025

Reproductive system of Eriocnema fulva Naudin (Melastomataceae), an endemic species of Minas Gerais state, SE Brazil

Eriocnema fulva Naudin is a perennial herb, endemic to Minas Gerais state, SE Brazil, found on humid, shaded rocky riverbanks in montane semideciduous seasonal forests. The species is threatened, but information regarding its biology is still lacking, although such information is fundamental to any management plan. We aimed to evaluate the reproductive system of Eriocnema fulva in the Jambreiro Forest (19° 58'-59' S and 43° 55'-52' W, 800-1100 m altitude), municipality of Nova Lima, by experiments carried out in 1997 and 1998. The flowers are white, and flowering is of the steady state type, occurring once a year from November to December. Anthers are poricidal, and pollen is the only resource for visitors. The chromosome number is n = 17 during meiosis. The species is self-compatible, but does not produce fruits by spontaneous self-pollination or agamospermy; it requires pollen vectors and buzz pollination in order to produce fruits. Cross-pollination is the main reproductive strategy of E. fulva, and is accentuated by the small number of flowers (one or two in each plant) opened per day. Although the population studied was shaded by forest canopy, the seeds needed light to germinate. Germination ratio was lower in germination cabinet on filter paper (14% after 30 days) than in greenhouse on soil brought from the forest (47% after 25 days). Although the fruit is a capsule and the seeds are small, dispersion (anemochory or hydrochory) does not seem to occur at long distance, as it is the case for other Melastomataceae species with similar syndrome