Search

Genetic variation in 27 populations of Ulex species from southern Spain and northern Morocco (Betic-Rif arc) was assessed using 11 chloroplast microsatellite (cpSSR) markers, which revealed 47 different haplotypes. These nonrecombinant, haploid markers allow measurement of genetic variation in closely related species of Ulex where molecular phylogenetic analyses have not provided a clear view of interspecific relationships. Discriminant analysis indicates that the haplotypes are useful to differentiate among species, and analysis of molecular variance (AMOVA) shows high levels of differentiation among populations. The minimum spanning tree (MST), that represents the connections between the haplotypes, suggests that the eastern Rifean U. africanus haplotypes are more genetically related than those from southern Spain. The latter may have lost genetic diversity while colonizing new habitats, eventually differentiating entiating into U. baeticus and U. scaber. Hybridization between these populations, followed by polyploidization, may have originated the tetraploids (U. congestus and U. borgiae) that colonized new habitats associated with acidic rocks. Separate groupings of U. scaber populations may indicate multiple origins from different stocks. Diversification in this group of Ulex species could be related to the opening of the Alboran Sea by Middle Miocene, when the populations from Morocco and Spain became isolated ,torn each other. Key words: chloroplast microsatellitcs; cpSSRs; genetic variation; Leguminosae; northern Morocco; southern Spain; Ulex.

For an introduced plant species to become invasive, it must be able to reproduce even in initially small populations. We tested for Allee effects (reduced reproductive performance of individuals in small populations) in the nonclonal, buzz-pollinated shrub Senna didymobotrya in its invasive range in South Africa. The species is self-compatible, but we found that in its invasive range in South Africa it requires pollinators to set seed. Nearly all stigmas (90%) received pollen, but natural fruit set was very low (3-20%). Pollen receipt and fruit set were not significantly correlated with population size. We thus found no evidence for an ecological Allee effect arising from pollen limitation in small populations. Offspring seedling performance, measured in terms of stem volume and leaf area, was also not significantly correlated with the number of plants in the source population, indicating that genetic Allee effects, such as inbreeding depression, are either absent or of such a small magnitude that they would be unlikely to limit further spread of S. didymobotrya in South Africa. Key words: alien plant; Baker's rule; Cassia didymobotrya; nonindigenous plant; pollination; population size; Xylocopa spp.

Legumes are simultaneously one of the largest families of crop plants and a cornerstone in the biological nitrogen cycle. We combined molecular and phylogenetic analyses to evaluate genome conservation both within and between the two major clades of crop legumes. Genetic mapping of orthologous genes identifies broad conservation of genome macrostructure, especially within the galegoid legumes, while also highlighting inferred chromosomal rearrangements that may underlie the variation in chromosome number between these species. As a complement to comparative genetic mapping, we compared sequenced regions of the model legume Medicago truncatula with those of the diploid Lotus japonicus and the polyploid Glycine max. High conservation was observed between the genomes of M. truncatula and L. japonicus, whereas lower levels of conservation were evident between M. truncatula and G. max. In all cases, conserved genome microstructure was punctuated by significant structural divergence, including frequent insertion/deletion of individual genes or groups of genes and lineage-specific expansion/contraction of gene families. These results suggest that comparative mapping may have considerable utility for basic and applied research in the legumes, although its predictive value is likely to be tempered by phylogenetic distance and genome duplication.

The 5S and the 18S-25S rRNA genes were physically mapped by fluorescent in situ hybridization (FISH) in all botanical varieties of cultivated peanut Arachis hypogaea (2n = 4x = 40), in the wild tetraploid A. monticola, and in seven wild diploid species considered as putative ancestors of the tetraploids. A detailed karyotype analysis including the FISH signals and the heterochromatic bands was carried out. Molecular cytogenetic landmarks are provided for the construction of a FISH-based karyotype in Arachis species. The size, number, and chromosome position of FISH signals and heterochromatic bands are similar in all A. hypogaea varieties and A. monticola, but vary among the diploid species. Genome constitution of the species is discussed and several chromosome homeologies are established. The bulk of the chromosome markers mapped, together with data on geographical distribution of the taxa, suggest that peanut originated upon domestication of A. monticola and evidence that the diploids A. duranensis and A, ipaensis are the most probable ancestors of both tetraploid species. Allopolyploidy could have arisen by a single event or, if by multiple events, always from the same diploid species. Key words: Arachis; FISH mapping: heterochromatin: karyotypes: Leguminosae; peanut origin: rRNA genes.

Byline: Won Kyung Lee (1), Toru Tokuoka (2), Kweon Heo (1) Keywords: Caesalpinioideae; Echinosophora; Embryology; Molecular phylogeny; rbcL; Sophora; trnL Intron Abstract: Although Echinosophora Nakai has been known as a monotypic and endemic genus of Papillionoideae of Fabaceae in Korea, it has been controversial whether it is distinct from or merged with Sophora. To resolve this matter, we conducted molecular phylogenetic analyses using nucleotide sequence data from the plastid rbcL gene and trnL (UAA) intron. Parsimony analysis, using a total of 53 taxa of the Papillionoideae (including E. koreensis [Nakai] Nakai and several species of Sophora and related genera) and using 20 taxa of Caesalpinioideae and Mimosoideae as outgroups, showed that, although the examined species of Sophora are split into two clades, E. koreensis formed a common clade with S. tomentosa (the type species of the genus) and S. flavescens. E. koreensis therefore should be treated as S. koreensis Nakai, and the generic name Echinosophora be eliminated. We also investigated the embryology of S. koreensis (=E. koreensis) and S. flavescens and found that no differences existed between them. Our molecular study, like other studies, strongly suggested that Sophora is polyphyletic. In this study we presented a summary of embryological features of the core Sophora for future critical comparison with related and unrelated taxa. Author Affiliation: (1) Division of Applied Plant Sciences, Kangwon National University, 200-701, Chuncheon, Korea (2) Department of Natural Environmental Sciences, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan Article History: Registration Date: 11/03/2004 Received Date: 31/10/2003 Accepted Date: 01/03/2004 Online Date: 09/04/2004

In wild-type Rhizobium leguminosarum, the sitABCD operon specifies a [Mn.sup.2+] transporter whose expression is severely reduced in cells grown in the presence of this metal. Mutations in the R. leguminosarum gene, mur (manganese uptake regulator), whose product resembles the Fur transcriptional regulator, cause high-level expression of sitABCD in the presence of [Mn.sup.2+]. In gel-shift mobility assays, purified R. leguminosarum Mur protein bound to at Least two regions near the sitABOD promoter region, although this DNA has no conventional consensus Fur-binding sequences (fur boxes). Thus, in contrast to [gamma]-proteobacteria, where Fur binds [Fe.sup.2+], the R. leguminosarum Fur homologue, Mur, act as a [Mn.sup.2]-responsive transcriptional regulator.

Synthesis of the Rhizobium leguminesarum [NiFe] hydrogenase requires the participation of 16 accessory genes (hupCDEFGHIJKhypABFCDEX) besides the genes encoding the structural proteins (hupSL). Transcription of hupSL is controlled by a -24/-1 2-type promoter ([P.sub.1]), located upstream of hupS and regulated by NifA. In this work, a second -24/-1 2-type promoter ([P.sub.3]), located upstream of the hupG gene and transcribing hupGHU genes in R. leguminosarum pea (Pisum sativum L.) bacteroids, has been identified in the hup gene cluster. Promoter [P.sub.3] was also active in R. leguminesarum free-living cells, as evidenced by genetic complementation of hydrogenase mutants. Both NifA and NtrC activated Ps expression in the heterologous host Klebsiella pneumoniae. Also, [P.sub.3] activity was highly stimulated by K. pneumoniae NifA in Escherichia coil. This NifA activation of [P.sub.3] expression only required the [[sigma].sup.54]-binding site, and it was independent of any cis-acting element upstream of the 54 box, which suggests a direct interaction of free NifA with the RNA polymerase holoenzyme. [P.sub.3]-dependent hupGHIJ expression in pea nodules started in interzone II/III, spanned through nitrogen-fixing zone III, and was coincident with the NifA-dependent nifH expression pattern. However, [P.sub.3] was dispensable for hupGHIJ transcription and hydrogenase activity in pea bacteroids due to transcription initiated at [P.sub.1]. This fact and the lack of an activator recruitment system suggest that [P.sub.3] plays a secondary role in symbiotic hupGHIJ expression.

Acacia aroma and A. macracantha are closely related species that inhabit northern and central Argentina. The reproductive barriers between them seem to be weak. They exhibit low genetic differentiation, high levels of interspecific gene flow, and extensive areas of sympatry. Isoenzymatic approaches were used to evaluate the population structure and mating system parameters in natural Argentine populations of A. aroma and A. macracantha and to provide new tools for the analysis of relationships between these two species. All studied populations had high levels of genetic variability and no significant departures from Hardy-Weinberg expectations, but the two species did not differ from each other. Most variability occured within populations. Mating system analysis showed high levels of outcrossing, no biparental inbreeding, and a high probability that individuals within progeny arrays are full rather than half sibs. In all A. aroma and A. macracantha populations, polymorphic loci had the same allelic variants, and no geographic or genetic isolation between species was found. The results favor the hypothesis that these two entities represent a single polymorphie species rather than two distinct species. Key words: Acacia; Argentina; Fabaceae; genetic variability; isozymes; mating system parameters; population structure.

Following the initial discovery of two legume-nodulating Burkholderia strains (L. Moulin, A. Munive, B. Dreyfus, and C. Boivin-Masson, Nature 411:948-950, 2001), we identified as nitrogen-fixing legume symbionts at least 50 different strains of Burkholderia caribensis and Ralstonia taiwanensis, all belonging to the [beta]-subclass of proteobacteria, thus extending the phylogenetic diversity of the rhizobia. R. taiwanensis was found to represent 93% of the Mimosa isolates in Taiwan, indicating that [beta]-proteobacteria can be the specific symbionts of a legume. The nod genes of rhizobial [beta]-proteobacteria ([beta]-rhizobia) are very similar to those of rhizobia from the [alpha]-subclass ([alpha]-rhizobia), strongly supporting the hypothesis of the unique origin of common nod genes. The [beta]-rhizobial nod genes are located on a 0.5-Mb plasmid, together with the nifH gene, in R. taiwanensis and Burkholderia phymatum. Phylogenetic analysis of available nodA gene sequences clustered [beta]-rhizobial sequences in two nodA lineages intertwined with [alpha]-rhizobial sequences. On the other hand, the [beta]-rhizobia were grouped with free-living nitrogen-fixing [beta]-proteobacteria on the basis of the nifH phylogenetic tree. These findings suggest that [beta]-rhizobia evolved from diazotrophs through multiple lateral nod gene transfers.

The anomalous systematic position of Swartzieae at the base of Papilionoideae is correlated with unusual developmental features: one petal or none; a ring meristem; polystemony; heterostemony; little or no alignment of stamens as antesepalous or antepetalous; multicarpely; and absence of unidirectional order of organs except in the calyx. Symmetry is zygomorphic throughout development. Floral ontogeny of four species of Swartzia reveals five sepals are initiated successively, beginning abaxially, but intercalary growth below the separate sepals forms a tubular calyx that splits irregularly, a feature typifying the genus. A single petal is initiated adaxially or may be missing altogether (in S. sericea). The apex enlarges and forms a ring meristem concurrently with carpel initiation. Several large-stamen primordia (2-15, according to the species) initiate first on the ring, followed by 40-150 small-stamen primordia. The latter initiate in centrifugal order in S. aureosericea and S. laurifolia or in acropetal order in S. sericea and S. madagascariensis. While ring meristems are considered to be homologous among Neotropical species studied as well as in the African S. madagascariensis, they vary in extent, duration, order of initiation, and productivity. Swartzieae is unlikely to be ancestral to the rest of Papilionoideae, based on radically differing floral ontogeny in the two groups. Key words: Bobgunnia; development; Fabaceae; flower; initiation; Leguminosae; Papilionoideae; ring meristem; ontogeny; polystemony; Swartzia; Swartzieae.

The karyotypes of 10 species and one variety of South American Lathyrus were determined and compared with those obtained of five entities from the Northern Hemisphere. Although all the species have a chromosome number of 2n = 14, they could be differentiated by their karyotype formula and quantitative parameters of the karyotypes. Phenetic distance and principal component analysis showed that in spite of the differences observed among entities, they can be grouped in clusters that coincide with the taxonomic sections established by F. K. Kupicha and with the life cycle of the species. South American species form a homogeneous group and can be distinguished by the presence of a subtelocentric pair, which has a macrosatellite in the long arm, and the lack of a short metacentric pair characteristic of most species of the Northern Hemisphere. From an evolutionary point of view, variation in total chromosome length without major changes in the karyotype formula suggests that changes in the amounts of genomic DNA are proportional to the relative length of each chromosome arm and that species of Notolathyrus evolved in a concerted fashion. Variation in genome size, however, is congruent with morphological variation of some reproductive organs as well as with the life cycle and minimum generation time, as predicted by the nucleotype hypothesis. Key words: concerted evolution; karyotypes; Lathyrus; Leguminosae; Notolathyrus; nucleotypes; South America.

To set up an in situ conservation strategy for Phaseolus lunatus, we analyzed the genetic structure of 29 populations in the Central Valley of Costa Rica. Using 22 enzyme loci, we quantified the proportion of polymorphic loci ([P.sub.p]), the mean number of alleles per locus (A), and the mean effective number of alleles per locus ([A.sub.o]), which equaled to 10.32%, 1.10, and 1.05, respectively. The total heterozygosity ([H.sub.T), the intrapopulation genetic diversity ([H.sub.s]), and the interpopulation genetic diversity ([D.sub.ST) were 0.193, 0.082, and 0.111, respectively. The genotypic composition of the analyzed populations showed a deviation from the Hardy-Weinberg proportions ([F.sub.IT] = 0.932). This disequilibrium was due to either genetic differentiation between populations ([F.sub.ST] = 0.497) or nonrandom mating within populations ([F.sub.IS] = 0.866). From the level of genetic differentiation between populations and the private alleles frequencies estimates, gene flow was calculated: [Nm.sub.w] = 0.398 and [Nm.sub.s] = 0.023, respectively. The results suggested that wild Lima bean maintains most of its isozyme variation among populations. Significant positive correlation was observed between population size and [P.sub.p], A, and [H.sub.o] (observed heterozygosity), whereas no correlation was observed with the average fixation index of population (F). The loss of genetic variability in populations was attributed to inbreeding and the bottleneck effects that characterized the target populations. In situ conservation and management procedures for wild Lima bean arc discussed. Key words: Costa Rica; Fabaceae; gene flow; genetic diversity; in situ conservation; isozymes; Lima bean; Phaseolus lunatus; population size.

We used nucleotide sequences from the internal transcribed spacers and 5.85 gene of nuclear ribosomal DNA to test competing phylogenetic and biogeographic hypotheses in Gleditsia. Eleven of 13 Gleditsia species were sampled, along with two species of its sister genus, Gymnocladus. Analyses of ITS data and of a combined data set that included sequences of ITS and two chloroplast genes supported several conclusions that were interpreted in light of fossil data and current legume phylogeny. Gleditsia and Gymnocladus appear to have originated in eastern Asia during the Eocene. Eastern North American species of both genera most likely evolved from ancestors that migrated across the Bering land bridge, but the eastern Asian/eastern North American disjunction appears to be much older in Gymnocladus than in Gleditsia. Gleditsia amorphoides, from temperate South America, is sister to the rest of the genus, suggesting early long-distance dispersal from Asia. The remainder of Gleditsia is divided into three unresolved clades, possibly indicating a split early in the evolution of the genus. Two of those clades contain only Asian species, and one contains Asian and North American species. The North American species, Gleditsia triacanthos and Gleditsia aquatica, are polymorphic and paraphyletic with respect to their ITS and cpDNA sequences, which suggests recent diversification. Key words: biogeography; Gleditsia; Gymnocladus; internal transcribed spacer; Leguminosae; molecular phylogeny; ribosomal DNA.

Cultivated soils often are either deficient or possess toxic concentrations of one or more mineral elements that adversely affect emergence, growth, maturity, production potential, and/or nutritional quality of common bean (Phaseolus vulgaris L.). Our objective was to study the inheritance of resistance to soil Zn deficiency. The resistant `Matterhorn' was crossed with the susceptible `T-39'. The [F.sub.1] was backcrossed to Matterhorn (B[C.sub.1]) and T-39 (B[C.sub.2]), and advanced to the [F.sub.2]. The two parents, [F.sub.1], [F.sub.2], B[C.sub.1], and B[C.sub.2] were evaluated in a Zn deficient field trial at Kimberly, Idaho in 2001. Plants were classified as tall-healthy or stunted with chlorotic leaves. Leaves were sampled from the two types of plants at flowering and analyzed for Zn concentration. The tall plants had an average leaf Zn concentration of 22.5 mg [kg.sup.-1]. In contrast, stunted plants had a Zn concentration of 15.0 mg [kg.sup.-1] All [F.sub.1] plants were tall resembling Matterhorn, except that unlike Matterhorn (white flowers and seeds) they had purple flowers and black shiny seeds. Thus, the resistance to Zn deficiency was dominant. A segregation of 45 resistant (R) to 20 susceptible (S) plants was observed in the [F.sub.2], giving a good fit to 3 R:1 S ([chi square] = 1.1538, P = 0.28). All plants in B[C.sub.1]were resistant. In B[C.sub.2], 142 R and 139 S plants were observed, giving a ratio of 1 R to 1 S ([chi square] = 0.032, P = 0.86). This supports a single dominant gene controlling soil Zn deficiency resistance. The symbol Znd is proposed for the dominant allele controlling resistance to soil Zn deficiency, and znd for its susceptible counterpart., AS MUCH AS 60% of the soils in the common bean production regions around the world suffer from mineral deficiencies or toxicities (CIAT, 1992; Thung and Rao, 1999; Wortmann et [...]