Novel Phaseolin types in wild and cultivated common bean (Phaseolus vulgaris,Fabaceae)

Forty-one wild types and 41 cultivars of common bean (Phaseolus vulgaris) from Meso-and South America were screened for variability of phaseolin seed protein using one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) and two-dimensional isoelectric focusing SDS/PAGE. Wild accessions from the Andean region showed phaseolin types which had not been previously identified in wild material from that region. Other wild accessions from Argentina exhibited novel phaseolin patterns collectively designated as ‘J’ (‘Jujuy’) phaseolin types, and one accession from northern Peru exhibited a novel phaseolin type, the ‘I’ (‘Inca’) type. The ‘H’ and ‘C’ phaseolins, previously identified only in cultivars, were observed in several wild accessions from Argentina. Among cultivars, two minor variants of the ‘S’ phaseolin type were identified. The ‘Sb’ (‘S Brazil’) was characteristic of a limited number of cultivars from Brazil whereas the ‘Sd’ (‘S Durango 222’) predominated in cultivars of the Mexican central highlands. The distribution of the previously described ‘B’ phaseolin appeared to be larger than formerly known as it extended not only in Colombia but also in Central America. It is possible to correlate the ‘Sb’, ‘Sd’, and ‘B’ phaseolin types with certain agronomic traits.     

Phaseolin seed variability in common bean (Phaseolus vulgaris L.) by capillary gel electrophoresis

Phaseolin, the major seed storage protein of Phaseolus vulgaris from forty-four wild and cultivated accessions, was studied using sodium dodecyl sulphate-capillary gel electrophoresis (SDS-CGE). In total, eleven phaseolin profiles, revealing polypeptide subunit variation in the range from 45.6 kDa to 54.4 kDa, were recorded. The number of polypeptide subunits recorded in particular profiles varied from 3 to 6; in total, eight phaseolin subunits were distinguished in the examined material. Ferguson plot analysis was used to correct non-ideal behaviour of phaseolin polypeptide subunits in capillary gel electrophoresis in the presence of SDS. The obtained results are compared to electrophoretic data received by slab polyacrylamide gel electrophoresis. The SDS-CGE method appears to provide a powerful tool for disclosure of phaseolin subunit variability.     

Variability in Andeannuña common beans (Phaseolus vulgaris,Fabaceae)

Nuñas are a group of common bean (Phaseolus vulgaris, Fabaceae) varieties, whose grains are consumed after toasting in their original Andean habitats. Nowadays, these varieties are restricted to certain parts of the highlands of Peru and Bolivia. Linguistic, ethnobotanical, and archaeological data suggest that they were grown in that zone duringpre-Hispanic times. SDS-PAGE electrophoresis shows a wide range ofphaseolin types amongnuñas, many of which are present in sympatric wild forms. This paper discusses the possibility thatnuñas resulted from an early and widely applied selection pressure during bean domestication in the Andes.     

Patterns of variation in cultivated common bean (Phaseolus vulgaris,Fabaceae)

More than 18,000 accessions of common bean (Thaseolus vulgaris, Fabaceae) from the Centro Internacional de Agricultura Tropical (CIAT) germplasm bank were examined at two locations in Colombia. A large variation in cultivated dry bean was found among accessions from primary centers of domestication in Middle and South America. For some bean types, such as medium- and large-seeded white, variation was greater among germplasm from western Asia (Turkey) and Europe (Portugal, Spain, Greece, France, Italy, and Bulgaria). Based on growth habit, on seed, pod, and leaf characteristics, and on ecological regions of adaptation, dry-bean germplasm was divided into a total of six gene pools from Middle American and four gene pools from South American centers of domestication. Most of the variation in the snap or stringless bean appears to be of relatively recent origin; it was greatest among cultivars from China, Europe, and the United States. These could be grouped into two additional gene pools. A strategy for breeding and transfer of genes across gene pools is also discussed.     

Isolation and characterization of lectins from kidney beans (Phaseolus vulgaris)

The bioactive properties of lectins obtained from raw and canned red kidney bean (Phaseolus vulgaris) were studied to determine the changes in their bioactivity during the canning process. Phytohaemagglutinin (PHA) was extracted using Affi-gel Blue gel and thyroglobulin-Sepharose and had a molecular weight of 32 kDa. Both the raw and the canned kidney beans possessed the ability to agglutinate red blood cells and inhibit α-glucosidase. The activity found in the canned beans was similar to that from the in the raw kidney beans. However, the amount of lectin that could be extracted from thyroglobulin-Sepharose was much less in the canned samples than in the raw kidney bean samples. The extracted lectin from the raw kidney beans was also subjected to a heating and cooling treatment using a differential scanning calorimeter. The lectin had a nonset denaturation temperature of 77.76 °C and it did not renature upon cooling. In this study, we demonstrated that extracts from raw red kidney bean and canned red kidney bean contain bioactive compounds capable of inhibiting HIV-1 RT in vitro.     

Nitrate reductase and nitrogenase activities of common beans (Phaseolus vulgaris L.) from different geographic locations

Summary Cultivars ofPhaseolus vulgaris (L.) from contrasting geographic locations were cultivated under fields conditions for measurements of nitrogenase and nitrate reductase activities. A first trial with two cultivars indicated that a tropical cultivar B-789 has a higher nitrogenase activity than a temperate one Elsa. And the converse was true for the nitrate reductase activity. While where a post flowering application was made, a renewal of nitrate reductase activity occurred. Further similar comparisons of both enzymatic activities upon eight tropical and temperate cultivars of equivalent vegetative cycles indicated, on the average, that tropical cultivars have a higher level of (C₂H₂) reduction and a lower nitrate reductase activity than temperature cultivars. These observations suggest that there exists an inverse relationship between the two enzymatic activities in common beans, and there probably exists genetic variability for a possible improvement of N-fixation ability. An early application of N-fertiliser upon the Elsa and B-789 plots promotes later nitrogenase activity while a post flowering application shows obvious a renewal of nitrate reductase activity. Thus, analyses of nitrate reductase and nitrogenase activities of a common bean crop at different physiological stages may give us an indication of the best time to apply supplementary nitrogen fertilisation to common beans to increase seed yield.     

Heterosis for chiasma frequency and quantitative traits in common beans (Phaseolus vulgaris L.)

Summary Ten genotypes, including inbreds, hybrids, and advanced populations, were examined in order to elucidate the relationship between position and frequency distribution of chiasmata and quantitative traits, including yield heterosis in common beans. The hybrid and advanced population groups were determined to possess 83% and 54% increased chiasma frequency, respectively in contrast to inbred lines. The increase in chiasma frequency of these populations was further manifested in a high number of interstitial chiasmata. The regular and superior chromosome behaviour of the hybrids was found to be positively associated with quantitative measures on bean yield, harvest index and bean yield efficiency. The results were discussed from the point of view that: a) increased interstitial chiasmata may provide an effective mechanism for maintaining genetic diversity and heterosis in hybrid populations; and b) heterosis for chiasma frequency and quantitative traits may be due to dispersed genes on the chromosomes having combined intra-and interallelic interactions. The data provide evidence for the existence of positive associations between interstitially localized chiasmata with its recombination potential and regular chromosome behaviour to bean yield heterosis. The role of enhanced interstitial chiasmata to promote higher levels of genetic variation and heterozygous advantage is discussed.     

Molecular ecology and selection in the drought-related Asr gene polymorphisms in wild and cultivated common bean (Phaseolus vulgaris L.)

ABSTRACT: BACKGROUND: The abscisic acid (ABA) pathway plays an important role in the plants' reaction to drought stress and ABA-stress response (Asr) genes are important in controlling this process. In this sense, we accessed nucleotide diversity at two candidate genes for drought tolerance (Asr1 and Asr2), involved in an ABA signaling pathway, in the reference collection of cultivated common bean (Phaseolus vulgaris L.) and a core collection of wild common bean accessions. RESULTS: Our wild population samples covered a range of mesic (semi-arid) to very dry (desert) habitats, while our cultivated samples presented a wide spectrum of drought tolerance. Both genes showed very different patterns of nucleotide variation. Asr1 exhibited very low nucleotide diversity relative to the neutral reference loci that were previously surveyed in these populations. This suggests that strong purifying selection has been acting on this gene. In contrast, Asr2 exhibited higher levels of nucleotide diversity, which is indicative of adaptive selection. These patterns were more notable in wild beans than in cultivated common beans indicting that natural selection has played a role over long time periods compared to farmer selection since domestication. CONCLUSIONS: Together these results suggested the importance of Asr1 in the context of drought tolerance, and constitute the first steps towards an association study between genetic polymorphism of this gene family and variation in drought tolerance traits. Furthermore, one of our major successes was to find that wild common bean is a reservoir of genetic variation and selection signatures at Asr genes, which may be useful for breeding drought tolerance in cultivated common bean.     

Diversity of common beans (Phaseolus vulgaris,Fabaceae) and conditions of production in Aguascalientes,Mexico

This study analyzes the regional diversity of common beans (Phaseolus vulgaris, Fabaceae) in Aguascalientes, Mexico, in relation to local physical, biological, cultural, and socioeconomic factors. A close direct relationship between bean diversity and the physical and biological factors and a close inverse relationship between bean diversity and the cultural and socioeconomic factors was found. Greater bean diversity was found in areas under rainfed conditions with low-input traditional agriculture where farmers with low income cultivate a great number of local heterogeneous landraces to insure some production for home use in spite of environmental stress conditions. Reduced bean diversity is cultivated under irrigated conditions with high-input modern agriculture where farmers with high income grow a few uniform improved cultivars to obtain high yields for commercial purposes. A previous study showed greater morphological variation in the seed collected in the 1940s compared to that collected in 1984. The bean variants of 1984 showed significantly earlier maturation. These findings suggest the necessity of periodic studies for a better understanding of the dynamic process of evolution of beans under continuous ecological, cultural, and socioeconomic change.     

Absorption and translocation of Cd in bush beans (Phaseolus vulgaris)

A series of experiments was conducted to examine some factors affecting the absorption and translocation of Cd in young bean plants ( Phaseolus vulgaris L. cv. Bulgarian). Absorption of Cd by roots was reduced in the presence of other cations of increasing valency or ionic radii. Reduced absorption was also found in the presence of EDTA. Concentration of Cd in exudates from excised stems increased with increased passage of Cd solutions and approached the concentration in the external medium (4.5 μ M Cd). This was apparently associated with saturation of adsorption sites in the stems. The stem behaved as a cation exchange column resulting in a chromatographic distribution of Cd towards the top of the plant. These experiments indicate that Cd existed in the xylem fluid as a free or weakly complexed cation. Additional experiments showed that the total amount of Cd absorbed by bean plants was elevated by inducing higher transpiration rates. The effect of water flux on Cd transport indicated apoplastic flow to the stele.     

Iron bioavailability of common beans (Phaseolus vulgaris L.) intrinsically labeled with 59Fe

A radiobioassay was performed in rats with or without iron depletion to evaluate the iron bioavailability of diets enriched with common beans and with “multimixture”, a nutritional supplement based on parts of foods that are not usually eaten. The full-body ⁵⁹Fe level was determined after 5 h, the absorbed ⁵⁹Fe level was determined after 48 h, and the amount of ⁵⁹Fe retained was determined after 7 days. Iron bioavailability was assessed by the full-body radioactivity of the animals, determined using a solid scintillation detector. The iron bioavailability of common beans was higher in the iron-depleted animals (55.7%) than in the non-depleted animals (25.12%) because of the higher absorption rate in the iron-depleted animals. The multimixture did not influence dietary iron bioavailability. In addition, the iron bioavailability of common beans was similar to that observed in the standard source of iron for Wistar rats. Hence, common beans may be considered an adequate dietary iron source because of its high bioavailability.     

Nodule conductance varied among common bean (Phaseolus vulgaris) genotypes under phosphorus deficiency

Common bean genotypes BAT477, COCOT, DOR364, Flamingo, and NAG310 were inoculated with Rhizobium tropici CIAT899 and grown under phosphorus deficiency. This treatment induced a significant decrease in shoot and nodule growth that varied among genotypes from 35% to 57% and from 45% to 61%, respectively, whereas root biomass was less affected. Phosphorus deficiency affected differently the genotypes for nodule number and size, and the responses of nodulated-root O2 uptake (Conr) to raising rhizospheric PO2. From the later data, nodule conductance could be computed by dividing the slope of the regression of Conr as a function of external pO2 by nodule surface area. It is concluded that differences in nodule conductance are related to genotypic tolerance to P deficiency.     

Effects of low pH and aluminum stresses on common beans (Phaseolus vulgaris) differing in low-phosphorus and photoperiod responses

Using common beans differing greatly in the response to photoperiod and low-phosphorus (P) stress, we investigated their responses to acidity and aluminum (Al)toxicity and the relationship between Al tolerance and organic acid exudation under Al or low P stress. A genotype Ginshi was found to be sensitive to low pH treatment. When exposed to pH 4.5, serious curvature in the root tips of cv. Ginshi was observed; however, it was completely corrected by the application of 5 or 10 μmol/L AlCl3; increasing calcium (Ca) could ameliorate Al toxicity, but it could not correct root curvature at pH 4.5. Common beans showed significant differences in both root growth and Al tolerance, and the varieties from the Andes were more tolerant to Al toxicity than those from the Mesoamerican origin. In the presence of 50 μmol/L AlCl3,all the common bean genotypes exuded citrate, and a significant difference in the amounts of citrate was observed among genotypes. The genotypes originated in the Mesoamerica tended to release more citrate than other origins in the presence of Al. The P-inefficient genotype DOR364 exuded more citrate than the P-efficient genotype G19833 in the presence of 50 μmol/L AlCl3, whereas no organic acids were detected in root exudates under low-P stress. A reduction of citrate exudation in the DOR364, but a slight increase of citrate exudation in the G19833, was observed under Al stress after they were exposed to 6-d P starvation. These results suggest that different low-P or Al tolerance in common beans might not be associated with organic acid exudation.