Transcriptome analysis reveals biosynthesis and regulation of flavonoid in common bean seeds during grain filling.

The Andean domesticated common beans (Phaseolus vulgaris) are significant sources of phenolic compounds associated with health benefits. However, the regulation of biosynthesis of these compounds during bean seed development remains unclear. To elucidate the gene expression patterns involved in the regulation of the flavonoid pathway, we conducted a transcriptome analysis of two contrasting Chilean varieties, Negro Argel (black bean) and Coscorron (white bean), at three developmental stages associated with seed color change, as well as different flavonoid compound accumulations. Our study reveals that phenolic compound synthesis initiates during seed filling, although it exhibits desynchronization between both varieties. We identified 10,153 Differentially Expressed Genes (DEGs) across all comparisons. The KEGG pathway 'Flavonoid biosynthesis' showed enrichment of induced DEGs in Negro Argel (PV172), consistent with the accumulation of delphinidin, petunidin, and malvidin hexosides in their seeds, while catechin glucoside, procyanidin and kaempferol derivatives were predominantly detected in Coscorrón (PV24). Furthermore, while the flavonoid pathway was active in both varieties, our results suggest that enzymes involved in the final steps, such as ANS and UGT, were crucial, inducing anthocyanin formation in Negro Argel. Additionally, during active anthocyanin biosynthesis, the accumulation of reserve proteins or those related to seed protection and germination was induced. These findings provide valuable insights and serve as a guide for plant breeding aimed at enhancing the health and nutritional properties of common beans.

Investigating the influence of eco-friendly approaches on saline soil traits and growth of common bean plants (Phaseolus vulgaris L.).

Soil salinization significantly impacts agricultural lands and crop productivity in the study area. Moreover, freshwater scarcity poses a significant obstacle to soil reclamation and agricultural production. Therefore, eco-friendly strategies must be adopted for agro-ecosystem sustainability under these conditions. A study conducted in 2022 and 2023 examined the interaction effects of various soil mulching materials (unmulched, white plastic, rice straw, and sawdust) and chitosan foliar spray application (control, 250 mg L-1 of normal chitosan, 125 mg L-1 of nano chitosan, and 62.5 mg L-1 of nano chitosan) on the biochemical soil characteristics and productivity of common beans in clay-saline soil. Higher organic matter, available nutrient content, and total bacteria count in soils were found under organic mulching treatments (rice straw and sawdust). In contrast, the white plastic mulching treatment resulted in the lowest values of soil electrical conductivity (EC) and the highest soil water content. Conversely, chitosan foliar spray treatments had the least impact on the chemical properties of the soil. Plants sprayed with 62.5 mg L-1 of nano chitosan exhibited higher chlorophyll content, plant height, fresh weight of shoots and roots, seed yield, and nutrient content compared to other chitosan foliar spray applications. All treatments studied led to a significant reduction in fungal communities and Na% in plants. The combined effect of organic mulch materials and foliar spray application of 62.5 mg L-1 nano chitosan appeared to enhance biochemical saline soil properties and common bean productivity.

Investigating the combined effects of ß-sitosterol and biochar on nutritional value and drought tolerance in Phaseolus vulgaris under drought stress.

Climate change-induced drought stress decreases crop productivity, but the application of ß-sitosterol (BS) and biochar (BC) boosts crop growth and yield. A pot experiment was conducted to examine the effects of the alone and combined application of BS and BC on the growth and yield of Phaseolus vulgaris under drought stress. The synergistic application of BS and BC increased plant height (46.9cm), shoot dry weight (6.9g/pot), and root dry weight (2.5g/pot) of P. vulgaris plants under drought stress. The trend of applied treatments for photosynthetic rate remained as BC (15%)

Bioaccessibility of carotenoids, tocochromanols, and iron from common bean (Phaseolus vulgaris L.) landraces.

Common beans (Phaseolus vulgaris L.) are among the most important legumes for human nutrition. The aim of the present study was to characterize the composition and in vitro bioaccessibility of tocochromanols, carotenoids, and iron from 14 different landraces and 2 commercial common bean varieties. Phytic acid, dietary fiber, and total (poly)phenolic content were determined as factors that can modify the bioaccessibility of the studied compounds. Two carotenoids were identified, namely lutein (4.6-315 ng/g) and zeaxanthin (12.2-363 ng/g), while two tocochromanols were identified, namely γ-tocopherol (2.62-18.01 µg/g), and δ-tocopherol (0.143-1.44 µg/g). The iron content in the studied samples was in the range of 58.7-144.2 µg/g. The contents of carotenoids, tocochromanols, and iron differed significantly among the studied samples but were within the ranges reported for commercial beans. After simulated gastrointestinal digestion, the average bioaccessibility of carotenoids was 30 %, for tocochromanols 50 %, and 17 % for iron. High variability in the bioaccessible content yielded by the bean varieties was observed. Dietary fiber, phytic acid and total (poly)phenol contents were negatively correlated with the bioaccessibility of carotenoids, while iron bioaccessibility was negatively correlated with the total (poly)phenol content. The principal component analysis indicated that the bioaccessibility of lutein was the main variable involved in class separations. The composition of the food matrix plays an important role in the bioaccessibility of carotenoids, tocochromanols and iron from cooked beans.

Effect of graphene oxide on carbon and nitrogen metabolism and growth of kidney bean at flowering stage.

Graphene oxide (GO) is a novel nanomaterial being applied in different fields, but was less used as foliar fertilizer in agriculture. We conducted a pot experiment to analyze the effects of foliar spraying GO from 0 (control), 50 (T1), 100 (T2), 150 (T3) and 200 mg·L-1 (T4) on the morphogenesis and carbon and nitrogen metabolism of kidney bean plants during the initiation of flowering to clarify the physiological effects of foliar spraying GO. The results showed that dry matter accumulation, the content of photosynthetic pigments, soluble sugars of T1 to T4 treatments, were significantly increased by 40.7%-43.4%, 10.4%-80.7%, 6.4%-9.1% in kidney bean plants compared with CK treatment, respectively. T3 treatment performed the best. Meanwhile, the activities of sucrose phosphate synthase, acid converting enzyme and neutral converting enzyme of T3 and T4 treatments were increased by 25.7%-45.5%, 17.4%-28.6%, and 14.7%-20.1%, and the activities of nitrate reductase, glutamine synthetase, and glutamate synthetase of T2 and T3 treatments were increased by 8.1%-15.2%, 11.5%-25.0%, and 89.7%-93.1%, respectively. In conclusion, foliar spraying of appropriate GO in early flowering stage of kidney bean could increase the content of photosynthetic pigments, improve the level of photosynthetic carbon and nitrogen metabolism, and increase dry matter accumulation. T3 treatment (150 mg·L-1) was the most effective in this study.

Compositional Optimization for Miticidal Activity, Ecotoxicity, and Phytotoxicity of Rosmarinus officinalis Essential Oils as Biorational Pesticides.

Recognizing the challenges in using botanicals as sustainable pest control agents due to compositional variation, this study addresses the limitations of traditional component-based approaches such as Hewlett and Plackett or Wadley's models. Based on the assumption of noninteractivity among constituents, these models often fail to predict outcomes accurately due to dynamic intermolecular interactions. We introduce a whole mixture-based approach, employing a combination of experimental design and polynomial modeling. This technique accurately predicts miticidal activity on Tetranychus urticae, ecotoxicity on Daphnia magna, and phytotoxic activities on Phaseolus vulgaris of Rosemarinus officinalis essential oils with varying composition. The RMSE values from the polynomial model are 66.9 and 5.0 for miticidal activity and ecotoxicity, respectively, while they are much higher in component-based models, up to 1097.7 and 41.3, respectively. Additionally, we utilize multiobjective optimization algorithms to identify the optimal supplementary blending of oils and compounds. This strategy aims to maximize miticidal effectiveness while minimizing ecotoxicity and phytotoxicity. Our approach for predicting multicomponent mixture effects is likely to bridge the knowledge gap between research and commercialization.

Common Bean Suppresses Hepatic Ceramide Metabolism in a Mouse Model of Metabolic Dysfunction-Associated Steatotic Liver Disease.

Background/Objectives: The incidence of metabolic dysfunction-associated steatotic liver disease (MASLD), a condition linked to the ongoing obesity pandemic, is rapidly increasing worldwide. In turn, its multifactorial etiology is consistently associated with low dietary quality. Changing dietary macronutrient and phytochemical quality via incorporating cooked common bean into an obesogenic diet formulation has measurable health benefits on the occurrence of both obesity and hepatic steatosis in C57BL/6 mice. Methods: A cohort of C57BL/6 mice were randomized into experimental diets containing multiple dietary concentrations of common bean. The primary endpoint of this study was comparing metabolomic analyses from liver and plasma of different treatment groups. Additionally, RNA sequencing and protein expression analysis via nanocapillary immunoelectrophoresis were used to elucidate signaling mediators involved. Results: Herein, global metabolomic profiling of liver and plasma identified sphingolipids as a lipid subcategory on which bean consumption exerted significant effects. Of note, C16 and C18 ceramides were significantly decreased in bean-fed animals. Hepatic RNAseq data revealed patterns of transcript expression of genes involved in sphingolipid metabolism that were consistent with metabolite profiles. Conclusions: Bean incorporation into an otherwise obesogenic diet induces effects on synthesis, biotransformation, and degradation of sphingolipids that inhibit the accumulation of ceramide species that exert pathological activity. These effects are consistent with a mechanistic role for altered sphingolipid metabolism in explaining how bean inhibits the development of MASLD.

Complete genome sequence of lima bean endornavirus 1: a putative new member of the genus Alphaendornavirus (family Endornaviridae).

In this study, we completely sequenced the genome of a new member of the genus Alphaendornavirus, family Endornaviridae, from lima bean (Phaseolus lunatus), for which we propose the name "lima bean endornavirus 1" (LbEV1). The complete genome of LbEV1 consists of 15,265 nucleotides, including a stretch of 12 cytosine residues at its 3' end, and contains a long single open reading frame (ORF) coding for a 4980-aa-long polyprotein. Analysis of the polyprotein sequence revealed the presence of four conserved functional domains (in order from the N- to C-terminus): viral helicase 1, peptidase _C97, glycosyltransferase_GTB-type, and viral RNA-dependent RNA polymerase (RdRP). The LbEV1 polyprotein showed the highest amino acid sequence similarity (63% identity and 98% coverage) to Phaseolus vulgaris endornavirus 3 (PvEV3) and also showed 42% identity (95% coverage) to Geranium carolinianum endornavirus. Phylogenetic analysis based on the viral RdRp domain showed that LbEV1 belongs to a subclade within the genus Alphaendornavirus that includes three other viruses infecting plants of the genus Phaseolus.

Changes in Phenolic Composition and Bioactivities of Ayocote Beans under Boiling (Phaseolus coccineus L.).

Ayocote beans (Phaseolus coccineus L.) are a rich source of some bioactive molecules, such as phenolic compounds that exhibit antioxidant capacity that promote health benefits. Ayocote is mainly consumed after cooking, which can impact the antioxidant characteristics of the phenolic compounds responsible for some of its health benefits. Therefore, this study investigated the effects of boiling on the phenolic composition and bioactivities of ayocote beans before and after boiling. Boiling decreased the total phenolic content (70.2, 60.3, and 58.2%), total anthocyanin (74.3, 80.6, and 85.7%), and antioxidant activity (DPPH: 41.2, 46.9, and 59.1%; ORAC: 48.23, 53.6 and 65.7%) of brown, black, and purple ayocote beans, respectively. All the extracts also inhibited the activity of α-glucosidase with efficacy values from 29.7 to 87.6% and α-amylase from 25.31 to 56.2%, with moderate antiglycation potential (15.2 to 73.2%). Phenolic acids, anthocyanins, and flavonoid decreases were detected in boiled samples by HPLC-MS analysis. Although boiling reduced the phenolic compounds, bioactive compounds remained in a considerable content in boiled ayocote.

Targeted hydrothermally induced cell biopolymer changes explain the in vitro digestion of starch and proteins in common bean (Phaseolus vulgaris) cotyledons.

Digestion of macro-nutrients (protein and starch) in pulses is a consequence of the interplay of both extrinsic (process-related) and intrinsic (matrix-dependent) factors which influence their level of encapsulation and physical state, and therefore, their accessibility by the digestive enzymes. The current work aimed at understanding the consequences of hydrothermally induced changes in the physical state of cell biopolymers (cell wall, protein, and starch) in modulating the digestion kinetics of starch and proteins in common beans. The hydrothermal treatments were designed such that targeted microstructural/biopolymer changes occurred. Therefore, bean samples were processed at temperatures between 60 and 95 °C for 90 minutes. It was demonstrated that these treatments allowed the modulation of starch gelatinization, protein denaturation and cell separation. The specific role of hydrothermally induced starch gelatinization and protein denaturation, alongside enhanced cell wall permeability on the digestion kinetics of common bean starch and proteins is illustrated. For instance, bean samples processed at T > 70 °C were marked by higher levels of starch digestibility (Cf values above 47%) compared to the partially (un-)gelatinized samples (processed at T ≤ 70 °C) (Cf values below 35%). Similarly, samples processed at T > 85 °C exhibited significantly higher levels of protein digestibility (Cf values above 47%) resulting from complete protein denaturation. Moreover, increased permeability of the cell wall to digestive enzymes in these samples (T > 85 °C) increased levels of digestibility of both gelatinized starch and denatured proteins. This study provides an understanding of the potential use of hydrothermal processing to obtain pulse-based ingredients with pre-determined microstructural and nutritional characteristics.

Exploring bioactive compounds in chickpea and bean aquafaba: Insights from glycomics and peptidomics analyses.

The objective of this study was to identify bioactive oligosaccharides and peptides in the cooking water of chickpeas and common beans, known as aquafaba. The oligosaccharides stachyose, raffinose and verbascose were quantified by high-performance anion-exchange chromatography; 78 and 67 additional oligosaccharides were identified in chickpea and common bean aquafaba, respectively, by LC-MS/MS. Chickpea aquafaba uniquely harbored ciceritol and other methyl-inositol-containing oligosaccharides. In prebiotic growth assays, chickpea aquafaba oligosaccharides were differentially utilized, promoting growth of Limosilactobacillus reuteri DSM 20016 and Bifidobacterium longum subsp. infantis ATCC 15697, but not Lacticaseibacillus rhamnosus GG. Dimethyl labeling, along with LC-MS/MS, effectively differentiated α- and γ-glutamyl peptides, revealing the presence of several γ-glutamyl peptides known to possess kokumi and anti-inflammatory activities, including γ-Glu-Phe and γ-Glu-Tyr in chickpeas aquafaba and γ-Glu-S-methyl-Cys and γ-Glu-Leu in beans aquafaba. This work uncovered unique bioactive peptides and oligosaccharides in aquafaba, helping promote its valorization, food system sustainability, and future health-promoting claims.

Effect of post-harvest storage on the chemical and microstructural characteristics of the common bean (Phaseolus vulgaris L.).

Hard to cook is a textural defect that affects the nutritional quality of beans stored under adverse temperature and humidity conditions. This defect is related to intrinsic characteristics such as seed coat thickness, composition and microstructure. The aim of the present study was to evaluate the chemical and microstructural characteristics of common bean (Phaseolus vulgaris L.) during 270 days of post-harvest storage at 30 °C and 70% relative humidity. Microstructural analysis revealed alteration of the cotyledon cell wall and seed coat affecting seed viability and restricting seedling emergence. The seed coat thickness contraction from 105.79 µm to 97.35 µm (270 days). Changes are related with the protein bodies migration from cotyledons to seed coat. An increase in neutral detergent fiber and the presence of CaOx crystals were observed, which confer rigidity to the seed coat and affect water diffusion after 150 days causing permeability changes that contributed to seed hardening.

Antioxidant and Anti-Inflammatory Capacities of Three Dry Bean Varieties after Cooking and In Vitro Gastrointestinal Digestion.

The present study delved into the chemical composition, antioxidant, and anti-inflammatory properties of three dry edible beans: Black (BL), Great Northern (GN), and Pinto (PN). The beans were soaked, cooked, and subjected to in vitro gastrointestinal (GI) digestion. BL bean exhibited significantly higher gastric (42%) and intestinal (8%) digestion rates. Comparative assessment of soluble GI-digested fractions (<3 kDa) revealed that the GN bean exhibited the highest abundance of dipeptides (P < 0.05). The BL bean fraction displayed a 4-fold increase in tripeptides (P < 0.05). Both BL and PN bean fractions are high in essential free amino acids, flavonols, and derivatives of hydroxybenzoic acid when compared to the GN bean. All the beans exhibited the ability to mitigate TNF-α-induced pro-inflammatory signaling; however, the BL bean fraction was the most effective at lowering AAPH-induced oxidative stress in HT-29 cells, followed by the GN bean (P < 0.05). In contrast, a low antioxidant effect was observed with PN beans.

Adaptive gene loss in the common bean pan-genome during range expansion and domestication.

The common bean (Phaseolus vulgaris L.) is a crucial legume crop and an ideal evolutionary model to study adaptive diversity in wild and domesticated populations. Here, we present a common bean pan-genome based on five high-quality genomes and whole-genome reads representing 339 genotypes. It reveals ~234 Mb of additional sequences containing 6,905 protein-coding genes missing from the reference, constituting 49% of all presence/absence variants (PAVs). More non-synonymous mutations are found in PAVs than core genes, probably reflecting the lower effective population size of PAVs and fitness advantages due to the purging effect of gene loss. Our results suggest pan-genome shrinkage occurred during wild range expansion. Selection signatures provide evidence that partial or complete gene loss was a key adaptive genetic change in common bean populations with major implications for plant adaptation. The pan-genome is a valuable resource for food legume research and breeding for climate change mitigation and sustainable agriculture.

Integrative metabolomics and chemometrics depict the metabolic alterations of differently processed red kidney beans (Phaseolus vulgaris L.) and in relation to in-vitro anti-diabetic efficacy.

Red kidney beans (RKB) serve as a powerhouse packed with a plethora of largely unexplored extraordinary chemical entities with potential significance. However, their nutraceutical applications as a functional hypoglycemic food still lag behind and warrant further investigation. With a scope to optimize chemical and biological traits of RKB, green modification approaches (processing methods) seem inevitable. Accordingly, the current study offered the first integrative workflow to scrutinize dynamic changes in chemical profiles of differently processed RKB and their potential entanglements on diabetes mitigation using Ultra Performance Liquid Chromatography-mass spectrometry (UPLC-MS/MS) coupled with chemometrics. Different physical and biological processing treatments namely germination, fermentation, cooking and dehulling were preliminarily implemented on RKB. Complementarily, the concomitant metabolite alterations among differently processed RKB were monitored and interpreted. Next, an in-vitro α-amylase and α-glycosidase inhibitory testing of the differently processed samples was conducted and integrated with orthogonal projection to latent structures (OPLS) analysis to pinpoint the possible efficacy compounds. A total of 72 compounds spanning fatty acids and their glycerides, flavonoids, phenolic acids, amino acids, dipeptides, phytosterols and betaxanthins were profiled. Given this analysis and compared with raw unprocessed samples, it was found that flavonoids experienced notable accumulation during germination while both fermentation and dehulling approaches sharply intensified the content of amino acids and dipeptides. Comparably, Fatty acids, phytosterols and betaxanthins were unevenly distributed among the comparable samples. Admittedly, OPLS-DA revealed an evident discrimination among the processed samples assuring their quite compositional discrepancies. In a more targeted approach, kaempferol-O-sophoroside, quercetin, carlinoside and betavulgarin emerged as focal discriminators of sprouted samples while citrulline, linoleic acid, linolenoyl-glycerol and stigmasterol were the determining metabolites in cooked samples. Our efficacy experimental findings emphasized that the different RKB samples exerted profound inhibitory actions against both α-amylase and α-glycosidase enzymes with the most promising observations in the case of sprouted and cooked samples. Coincidently, OPLS analysis revealed selective enhancement of possible efficacy constituents primarily citrulline, formononetin, gamabufotalin, kaempferol-O-sophoroside, carlinoside, oleic acid and ergosterol in sprouted and cooked samples rationalizing their noteworthy α-amylase and α-glucosidase inhibitory activities. Taken together, this integrated work provides insightful perspectives beyond the positive impact of different processing protocols on bioactives accumulation and pharmacological traits of RKB expanding their utilization as functional hypoglycemic food to rectify diabetes.

Technical-functional and surface properties of white common bean proteins (Phaseolus vulgaris L.): Effect of pH, protein concentration, and guar gum presence.

Legumes are abundant sources of proteins, and white common bean proteins play an important role in air-water interface properties. This study aims to investigate the technical-functional properties of white common bean protein isolate (BPI) as a function of pH, protein concentration, and guar gum (GG) presence. BPI physicochemical properties were analyzed in terms of solubility, zeta potential, and mean particle diameter at pH ranging from 2 to 9, in addition to water-holding capacity (WHC), oil-holding capacity (OHC), and thermogravimetric analysis. Protein dispersions were evaluated in terms of dynamic, interfacial, and foam-forming properties. BPI showed higher solubility (>80 %) at pH 2 and above 7. Zeta potential and mean diameter ranged from 15.43 to -34.08 mV and from 129.55 to 139.90 nm, respectively. BPI exhibited WHC and OHC of 1.37 and 4.97 g/g, respectively. Thermograms indicated decomposition temperature (295.81 °C) and mass loss (64.73 %). Flow curves indicated pseudoplastic behavior, with higher η100 values observed in treatments containing guar gum. The behavior was predominantly viscous (tg δ > 1) at lower frequencies, at all pH levels, shifting to predominantly elastic at higher frequencies. Equilibrium surface tension (γeq) ranged from 43.87 to 41.95 mN.m-1 and did not decrease with increasing protein concentration under all pH conditions. All treatments exhibited ϕ < 15°, indicating predominantly elastic surface films. Foaming properties were influenced by higher protein concentration and guar gum addition, and the potential formation of protein-polysaccharide complexes favored the kinetic stability of the system.

Reduction of antinutrients and off-flavour in kidney bean flour by acidic and alkaline reactive extrusion.

The presence of antinutrients and undesirable flavours in kidney bean flour poses challenges to consumer acceptance. Although extrusion can mitigate antinutrients to some extent, its impact on reducing beany flavour in bean flour remains underexplored. This study investigated the effects of injecting acetic acid or sodium carbonate solutions at three concentration levels (0.05, 0.1, 0.15 mol/L), in conjunction with three temperature profiles (40/60/80/80/90, 40/60/80/90/110, 50/70/90/110/130 °C) and two feed moisture levels (25, 30 %), on the removal of antinutrients (condensed tannins, trypsin inhibitor activity, phytic acid, raffinose family oligosaccharides) and reduction of volatile compounds that contribute to beany flavour in whole kidney bean flour. The results showed that all concentrations of acetic acid and sodium carbonate solutions effectively reduced condensed tannins compared to water, especially at 130 °C extrusion temperature. Introducing acetic acid and sodium carbonate solutions at a concentration of 0.15 mol/L led to 72 and 90 % reduction of total raffinose family oligosaccharide content, respectively, in contrast to the 17 % reduction observed with water alone. The incorporation of sodium carbonate solution reduced the total volatile compounds by 45-58 % as compared with water (23-33 %) and acetic acid (11-27 %). This reduction was primarily due to the reduction of aldehydes, alcohols, and aromatic hydrocarbons. These results indicate that injecting sodium carbonate solution during extrusion can effectively reduce antinutrients and beany flavour compounds in kidney bean flour.

Potential Human Health Benefits of Phaseolus vulgaris L. var Venanzio: Effects on Cancer Cell Growth and Inflammation.

It is widely recognized that foods, biodiversity, and human health are strongly interconnected, and many efforts have been made to understand the nutraceutical value of diet. In particular, diet can affect the progression of intestinal diseases, including inflammatory bowel disease (IBD) and intestinal cancer. In this context, we studied the anti-inflammatory and antioxidant activities of extracts obtained from a local endangered variety of Phaseolus vulgaris L. (Fagiola di Venanzio, FV). Using in vitro intestinal cell models, we evaluated the activity of three different extracts: soaking water, cooking water, and the bioaccessible fraction obtained after mimicking the traditional cooking procedure and gastrointestinal digestion. We demonstrated that FV extracts reduce inflammation and oxidative stress prompted by interleukin 1ß through the inhibition of cyclooxygenase 2 expression and prostaglandin E2 production and through the reduction in reactive oxygen species production and NOX1 levels. The reported data outline the importance of diet in the prevention of human inflammatory diseases. Moreover, they strongly support the necessity to safeguard local biodiversity as a source of bioactive compounds.

Unearthing Optimal Symbiotic Rhizobia Partners from the Main Production Area of Phaseolus vulgaris in Yunnan.

Phaseolus vulgaris is a globally important legume cash crop, which can carry out symbiotic nitrogen fixation with rhizobia. The presence of suitable rhizobia in cultivating soils is crucial for legume cropping, especially in areas beyond the plant-host native range, where soils may lack efficient symbiotic partners. We analyzed the distribution patterns and traits of native rhizobia associated with P. vulgaris in soils of Yunnan, where the common bean experienced a recent expansion. A total of 608 rhizobial isolates were tracked from soils of fifteen sampling sites using two local varieties of P. vulgaris. The isolates were discriminated into 43 genotypes as defined by IGS PCR-RFLP. Multiple locus sequence analysis based on recA, atpD and rpoB of representative strains placed them into 11 rhizobial species of Rhizobium involving Rhizobium sophorae, Rhizobium acidisoli, Rhizobium ecuadorense, Rhizobium hidalgonense, Rhizobium vallis, Rhizobium sophoriradicis, Rhizobium croatiense, Rhizobium anhuiense, Rhizobium phaseoli, Rhizobium chutanense and Rhizobium etli, and five unknown Rhizobium species; Rhizobium genosp. I~V. R. phaseoli and R. anhuiense were the dominant species (28.0% and 28.8%) most widely distributed, followed by R. croatiense (14.8%). The other rhizobial species were less numerous or site-specific. Phylogenies of nodC and nifH markers, were divided into two specific symbiovars, sv. phaseoli regardless of the species affiliation and sv. viciae associated with R. vallis. Through symbiotic effect assessment, all the tested strains nodulated both P. vulgaris varieties, often resulting with a significant greenness index (91-98%). However, about half of them exhibited better plant biomass performance, at least on one common bean variety, and two isolates (CYAH-6 and BLYH-15) showed a better symbiotic efficiency score. Representative strains revealed diverse abiotic stress tolerance to NaCl, acidity, alkalinity, temperature, drought and glyphosate. One strain efficient on both varieties and exhibiting stress abiotic tolerance (BLYH-15) belonged to R. genosp. IV sv. phaseoli, a species first found as a legume symbiont.

PvMYB60 gene, a candidate for drought tolerance improvement in common bean in a climate change context.

BACKGROUND: Common bean (Phaseolus vulgaris) is one of the main nutritional resources in the world, and a low environmental impact source of protein. However, the majority of its cultivation areas are affected by drought and this scenario is only expected to worsen with climate change. Stomatal closure is one of the most important plant responses to drought and the MYB60 transcription factor is among the key elements regulating stomatal aperture. If targeting and mutating the MYB60 gene of common bean would be a valuable strategy to establish more drought-tolerant beans was therefore investigated. RESULTS: The MYB60 gene of common bean, with orthology to the Arabidopsis AtMYB60 gene, was found to have conserved regions with MYB60 typical motifs and architecture. Stomata-specific expression of PvMYB60 was further confirmed by q-RT PCR on organs containing stomata, and stomata-enriched leaf fractions. Further, function of PvMYB60 in promoting stomata aperture was confirmed by complementing the defective phenotype of a previously described Arabidopsis myb60-1 mutant. CONCLUSIONS: Our study finally points PvMYB60 as a potential target for obtaining more drought-tolerant common beans in the present context of climate change which would further greatly contribute to food security particularly in drought-prone countries.