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Dry bean (Phaseolus vulgaris L.) is highly susceptible to drought stress, and drought affects 60% of global bean production. We evaluated elite exotic dry bean germplasm derived from the Mesoamerican gene pool for drought tolerance, yield, and adaptation to western Nebraska during 2006 and 2007 at three research sites. Seven tropical lines were evaluated with two great northern cultivars (Matterhorn and BerylR) and one pinto cultivar (Bill-Z) serving as checks. Adjacent nonstressed (NS) and drought-stressed (DS) blocks were evaluated. Within each block, the selected lines were assigned to experimental units using a randomized complete block design with four replications at each location. On average, yield was 60% less, 100-seed weight was 19.2% lower, and maturity occurred 4 d earlier under DS than under NS conditions. Beryl-R, SER 22, and Matterhorn had the greatest average yield under both NS (3564, 3347, and 3440 kg [ha.sup.-1], respectively) and DS (1701, 1773, and 1584 kg [ha.sup.-1], respectively). These genotypes were also the most drought tolerant based on the drought susceptibility index (0.9, 0.8, and 0.9, respectively) and geometric mean (2462, 2436, and 2335, respectively). Based on these results, Matterhorn, Beryl-R, and SER 22 show the most promise for use in breeding for drought tolerance. doi: 10.2135/cropsci2008.12.0694

This analysis goes beyond many phylogenies in exploring how phylogenetic structure imposed by morphology, ecology, and geography reveals useful evolutionary data. A comprehensive range of such diversity is evaluated within tribe Indigofereae and outgroups from sister tribes. A combined data set of 321 taxa (over one-third of the tribe) by 80 morphological characters, 833 aligned nuclear ribosomal ITS/5.8S sites, and an indel data set of 33 characters was subjected to parsimony analysis. Notable results include the Madagascan dry forest Disynstemon resolved as sister to tribe Indigofereae, and all species of the large genus Indigofera comprise just four main clades, each diagnosable by morphological synapomorphies and ecological and geographical predilections. These results suggest niche conservation (ecology) and dispersal limitation (geography) are important processes rendering signature shapes to the Indigofereae phylogeny in different biomes. Clades confined to temperate and succulent-rich biomes are more dispersal limited and have more geographical phylogenetic structure than those inhabiting tropical grass-rich vegetation. The African arid corridor, particularly the Namib center of endemism, harbors many of the oldest Indigofera lineages. A rates analysis of nucleotide substitutions confirms that the ages of the oldest crown clades are mostly younger than 16 Ma, implicating dispersal in explaining the worldwide distribution of the tribe. Key words: biogeography; character evolution: dispersal limitation; Fabaceae; Indigofera; Indigofereae; Leguminosae; molecular phylogeny; rates analysis.

Little is known about the molecular mechanisms by which the embryo proper and suspensor of plant embryos activate specific gene sets shortly after fertilization. We analyzed the upstream region of the scarlet runner bean (Phaseolus coccineus) G564 gene to understand how genes are activated specifically within the suspensor during early embryo development. Previously, we showed that the G564 upstream region has a block of tandem repeats, which contain a conserved 10-bp motif ([GAAAAG.sup.C]/[sub.T]GAA), and that deletion of these repeats results in a loss of suspensor transcription. Here, we use gain-of-function (GOF) experiments with transgenic globular-stage tobacco embryos to show that only 1 of the 5 tandem repeats is required to drive suspensor-specific transcription. Fine-scale deletion and scanning mutagenesis experiments with I tandem repeat uncovered a 54-bp region that contains all of the sequences required to activate transcription in the suspensor, including the 10-bp motif (GAAAAGCGAA) and a similar 10-bp-like motif (GAAAAACGAA). Site-directed mutagenesis and GOF experiments indicated that both the 10-bp and 10-bp-like motifs are necessary, but not sufficient to activate transcription in the suspensor, and that a sequence (TTGGT) between the 10-bp and the 10-bp-like motifs is also necessary for suspensor transcription. Together, these data identify sequences that are required to activate transcription in the suspensor of a plant embryo after fertilization. promoter analysis | scarlet runner bean

Genetic diversity in 20 elite blackgram (Vigna mungo (L.) Hepper) genotypes was studied using microsatellite and AFLP markers. Thirty-six microsatellite markers from azuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) were successfully amplified across the 20 blackgram genotypes and 33 microsatellite markers showed polymorphism. A total of 137 microsatellite alleles were generated with an average of 4.1 alleles per locus. The number of alleles ranged from two to nine and the polymorphic information content value for the microsatellite markers varied from 0.10 to 0.87 with an average of 0.49. Microsatellite markers were highly informative and a combination of only three microsatellite markers (CEDG264, CEDG173, and CEDG044) was sufficient to discriminate all 20 blackgram genotypes. In the case of AFLP, 11 primer pairs generated 324 polymorphic marker fragments. The polymorphic information content values for AFLP primer combinations ranged from 0.21 to 0.34 with an average of 0.29. Similarity measures and clustering analyses were made using microsatellite and AFLP data separately. The resulting dendrograms distributed the 20 blackgram genotypes into five main clusters. The dendrograms were comparable with each other with the Mantel test between the cophenetic matrices of microsatellite data and AFLP data showing moderate correlation (r = 0.64). The results of the principal components analysis were well congruent with the dendrograms. In the dendrograms as well as in the principal components analyses, genotype Trombay wild (Vigna mungo var. silvestris) was placed separately from rest of the genotypes. This study demonstrated that the azuki bean microsatellite markers are highly polymorphic and informative and can be successfully used for genome analysis in blackgram. Results indicate that sufficient variability is present in the blackgram genotypes and would be helpful in the selection of suitable parents for breeding purposes and gene mapping studies. Key words: genetic diversity, blackgram, microsatellite markers, AFLP markers, genotype identification. La diversite genetique chez 20 genotypes elites du haricot mung a grains noirs (Vigna mungo (L.) Hepper) a ete etudiee a l'aide de microsatellites et de marqueurs AFLP. Trente-six marqueurs microsatellites provenant du haricot azuki (Vigna angularis (Wild.) Ohwi & Ohashi) ont amplifie avec succes chez les 20 genotypes elites du haricot mung a grains noirs et 33 de ceux-ci etaient polymorphes. Un ensemble de 137 alleles microsatellites ont ete observes pour une moyenne de 4,1 alleles par locus. Le nombre d'alleles variait entre deux et neuf tandis que l'indice de contenu d'information polymorphique pour ces marqueurs variait entre 0,10 et 0,87 pour une moyenne de 0,49. Les marqueurs microsatellites se sont averes tres informatifs et une combinaison de seulement trois marqueurs (CEDG264, CEDG173 et CEDG044) suffisait a distinguer les 20 genotypes. Dans le cas des AFLP, 11 paires d'amorces ont genere 324 fragments polymorphes. Les indices de contenu d'information polymorphique pour les AFLP allaient de 0,21 a 0,34 pour une moyenne de 0,29. Des mesures de similarite et des analyses de groupement ont ete effectuees a l'aide des donnees microsatellites et AFLP separement. Les dendrogrammes obtenus divisaient les 20 genotypes en cinq groupes principaux. Les dendrogrammes etaient semblables sur la base d'un test de Mantel effectue sur les matrices co-phenetiques des donnees microsatellites et AFLP, lequel montrait une correlation moderee (r = 0,64). Les resultats d'une analyse des composantes principales concordaient avec les dendrogrammes. Dans les dendrogrammes tout comme dans les analyses des composantes principales, le genotype Trombay wild (V. mungo var. silvestris) formait un groupe distinct des autres genotypes. Cette etude montre que les microsatellites du haricot azuki sont tres polymorphes et informatifs de sorte qu'ils sont utiles pour l'analyse du genome chez le haricot mung a grains noirs. Les resultats indiquent qu'une variabilite suffisante est presente au sein de ces genotypes et qu'elle serait utile en vue de la selection de parents appropries pour des fins de selection varietale et des etudes de cartographie genetique. Mots-cles: diversite genetique, haricot mung a grains noirs, marqueurs microsatellites, marqueurs AFLP, identification des genotypes. [Traduit par la Redaction], Introduction Grain legumes are among the most important crops in many countries, since they provide one third of the dietary protein for human consumption. Blackgram (Vigna mungo (L.) Hepper) is [...]

Prosopis represents a valuable forest resource in arid and semiarid regions. Management of promising species requires information about genetic parameters, mainly the heritability ([h.sup.2]) of quantitative profitable traits. This parameter is traditionally estimated from progeny tests or half-sib analysis conducted in experimental stands. Such an approach estimates [h.sup.2] from the ratio of between-family/total phenotypic variance. These analyses are difficult to apply to natural populations of species with a long life cycle, overlapping generations, and a mixed mating system, without genealogical information. A promising alternative is the use of molecular marker information to infer relatedness between individuals and to estimate [h.sup.2] from the regression of phenotypic similarity on inferred relatedness. In the current study we compared [h.sup.2] of 13 quantitative traits estimated by these two methods in an experimental stand of P. alba, where genealogical information was available. We inferred pairwise relatedness by Ritland's method using six microsatellite loci. Relatedness and heritability estimates from molecular information were highly correlated to the values obtained from genealogical data. Although Ritland's method yields lower [h.sup.2] estimates and tends to overestimate genetic correlations between traits, this approach is useful to predict the expected relative gain of different quantitative traits under selection without genealogical information. Key words: Fabaceae; heritability; Leguminosae; molecular markers; Prosopis alba; quantitative traits.

Tolerance to low P soils is a desirable trait in common bean (Phaseolus vulgaris L.) cultivars grown in acid-weathered soils. Genetic variability in response to P-deficient soils exists in the Andean gene pool. G19833, a low P-tolerant indeterminate Andean landrace, has been evaluated for quantitative trait loci (QTL) and tolerance to low P in combination with Mesoamerican parents. Our goal was to expand our understanding of phenotypic traits and QTL from G19833 expressed in an Andean background. An [F.sub.5:7] recombinant inbred line (RIL) population developed from two Andean bean genotypes, G19833 and AND696, a determinate line susceptible to low P soils, was examined under low and high soil P levels in replicated field trials. Phosphorus uptake was reduced by 70% and yield by 60% in low P compared to high P treatments. A linkage map was developed with 11 linkage groups and a total length of 1105 cM. Quantitative trait loci for root growth, seed yield, seed P content, and P use efficiency colocalized near the fin gene on linkage group B1. Quantitative trait loci for root growth traits, seed yield, and P uptake colocalized on B11. Quantitative trait loci for root length density (cm [cm.sup.-3]) and root surface area ([cm.sup.2]) did not colocalize with QTL for P uptake. This study indicates that root traits did not play an important role in tolerance to low P soil in an Andean x Andean cross, contrary to previous results with the same P-efficient Andean parent (G19833) crossed to a Mesoamerican bean genotype.

Sinorhizobium meliloti forms symbiotic, nitrogen-fixing nodules on the roots of Medicago truncatula. The bacteria invade and colonize the roots through structures called infection threads. S. meliloti unable to produce the exopolysaccharide succinoglycan are unable to establish a symbiosis because they are defective in initiating the production of infection threads and in invading the plant. Here, we use microarrays representing 16,000 M. truncatula genes to compare the differential transcriptional responses of this host plant to wild-type and succinoglycan-deficient S. meliloti at the early time point of 3 days postinoculation. This report describes an early divergence in global plant gene expression responses caused by a rhizobial defect in succinoglycan production, rather than in Nod factor production. The microarray data show that M. truncatula inoculated with wild-type, succinoglycan-producing S. meliloti more strongly express genes encoding translation components, protein degradation machinery, and some nodulins than plants inoculated with succinoglycan-deficient bacteria. This finding is consistent with wild-type-inoculated plants having received a signal, distinct from the well characterized Nod factor, to alter their metabolic activity and prepare for invasion. In contrast, M. truncatula inoculated with succinoglycan-deficient S. meliloti more strongly express an unexpectedly large number of genes in two categories: plant defense responses and unknown functions. One model consistent with our results is that appropriate symbiotically active exopolysaccharides act as signals to plant hosts to initiate infection thread formation and that, in the absence of this signal, plants terminate the infection process, perhaps via a defense response. nitrogen fixation | nodule | succinoglycan | rnicroarray | legume

Symbiotic nitrogen-fixing rhizobia are able to trigger root deformation in their Fabaceae host plants, allowing their intracellular accommodation. They do so by delivering molecules called Nod factors. We analyzed the patterns of nucleotide polymorphism of five genes controlling early Nod factor perception and signaling in the Fabaceae Medicago truncatula to understand the selective forces shaping the evolution of these genes. We used 30 M. truncatula genotypes sampled in a genetically homogeneous region of the species distribution range. We first sequenced 24 independent loci and detected a genomewide departure from the hypothesis of neutrality and demographic equilibrium that suggests a population expansion. These data were used to estimate parameters of a simple demographic model incorporating population expansion. The selective neutrality of genes controlling Nod factor perception was then examined using a combination of two complementary neutrality tests, Tajima's D and Fay and Wu's standardized H. The joint distribution of D and H expected under neutrality was obtained under the fitted population expansion model. Only the gene DMI1, which is expected to regulate the downstream signal, shows a pattern consistent with a putative selective event. In contrast, the receptor-encoding genes NFP and NORK show no significant signatures of selection. Among the genes that we analyzed, only DMI1 should be viewed as a candidate for adaptation in the recent history of M. truncatula.

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.

Within papilionoid legumes, characterized by flowers with strong bilateral symmetry, a derived condition within angiosperms, Cadia (Cadia purpurea) has reverted to radially symmetrical flowers. Here, we investigate the genetic basis of this morphological reversal. Two orthologues of the floral symmetry gene CYCLOIDEA (CYC) demarcate the adaxial (dorsal) region of the flower in typical papilionoid legumes. In the model legume Lotusjaponicus, one of these LegCYC genes has been shown, like CYC, to be required for the establishment of floral bilateral symmetry. This study shows that these genes are expressed in the adaxial region of the typical papilionoid flower of Lupinus, which belongs to the same papilionoid subclade as Cadia. In Cadia, these genes also are expressed, but the expression pattern of one of these has expanded from the adaxial to the lateral and abaxial regions of the corolla. This result suggests that the radial flowers of Cadia are dorsalized and, therefore, are not a true evolutionary reversal but an innovative homeotic transformation, where, in this case, all petals have acquired dorsal identity. This study raises a question over other putative reversals in animals and plants, which also may be cryptic innovations. developmental gene | floral evolution | CYCLOIDEA | Leguminosae (Fabaceae)