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Salinity stress significantly threatens seed germination, plant growth, and agricultural productivity, necessitating effective mitigation strategies. This study evaluates the potential of salicylic acid (SA) pretreatment to alleviate the detrimental effects of salinity on common bean ( Phaseolus vulgaris ) genotypes. SA, a phenolic plant hormone, is crucial for regulating growth, stress responses, and essential physiological processes, including seed germination and ion transport. Previous research has established the general benefits of SA in enhancing stress tolerance, but the specific mechanisms and effects on common bean genotypes remain underexplored. This research focuses on the impact of salinity on the germination and seedling growth of various common bean genotypes, the efficacy of SA pretreatment in enhancing these genotypes' tolerance to salinity stress, and the underlying physiological and biochemical mechanisms, particularly involving the antioxidant defense system. The research was conducted in two phases: germination and seedling growth. Ten genotypes and two commercial varieties were exposed to varying salinity levels alongside SA concentrations to assess germination performance. Subsequently, six genotypes and one variety were evaluated for seedling growth under controlled and salt stress conditions (100 mM and 200 mM NaCl), with SA treatments at 0, 0.5, and 1 mM. Results revealed that salinity severely impaired germination traits, which were significantly enhanced by SA pretreatment. During the seedling growth phase, salinity stress resulted in reduced protein, chlorophyll, and carotenoid content, decreased potassium (K⁺) levels, and diminished water content, while increasing electrolyte leakage, malondialdehyde (MDA) levels, sodium (Na⁺) concentrations, enzyme activities, and proline levels. Importantly, SA pretreatment elevated chlorophyll and protein concentrations, improved water retention, and moderated K⁺ and Na⁺ levels, including their ratios under stress conditions. SA pretreatment also significantly enhanced the antioxidant defense system, reducing oxidative damage induced by salinity stress. Principal component analysis (PCA) successfully categorized the genotypes into semi-tolerant, tolerant, semi-sensitive, and sensitive classes based on their stress responses. Notably, the Jules variety exhibited exceptional resilience during both germination and seedling growth stages, indicating its potential as a superior candidate for cultivation in salt-affected regions. This study highlights SA pretreatment as an effective strategy to enhance salinity stress resilience in common bean genotypes. The novelty of this work lies in the detailed elucidation of SA's role in modulating antioxidant defenses and ion homeostasis in different genotypes, providing new insights into breeding programs and agricultural practices aimed at improving crop resilience and productivity in increasingly saline environments.

Essential oils (EO) of several plant species have the potential to combat plant and fungal diseases. However, the effects of Achillea millefolium EO on the development of common bean ( Phaseolus vulgaris L.), is still unknown. Moreover, its effect on N 2 -fixing bacteria, and in general on soil properties has not been studied yet. A greenhouse trial was set up to evaluate both the influence that Achillea millefolium EO and the inoculation with three different Rhizobium strains have on the bean plant and on the chemical and microbiological properties of an agriculturally used Cambisol. Non-inoculated pots were used as control. Our findings showed a decrease in bacterial colony forming units due to EO application and an increase following the Rhizobium inoculation compared to the control. The EO application decreased soil basal respiration and activities of dehydrogenase, urease, β-glucosidase and acid phosphatase. Such effects were stronger with higher oil concentrations. Moreover, the treatments combining Rhizobium inoculation with EO showed a positive effect on nodulation and plant height. Overall, the combined application of Achillea millefolium EO and rhizobia works as an efficient biocide that could be applied in organic agriculture without hampering the activity of nodule-forming N-fixing bacteria and the development of common bean.

The reactive oxygen species (ROS) generated by respiratory burst oxidative homologs (Rbohs) are involved in numerous plant cell signaling processes, and have critical roles in the symbiosis between legumes and nitrogen‐fixing bacteria. Previously, down‐regulation of RbohB in Phaseolus vulgaris was shown to suppress ROS production and abolish Rhizobium infection thread (IT) progression, but also to enhance arbuscular mycorrhizal fungal (AMF) colonization. Thus, Rbohs function both as positive and negative regulators. Here, we assessed the effect of enhancing ROS concentrations, by overexpressing PvRbohB, on the P. vulgaris–rhizobia and P. vulgaris–AMF symbioses. We estimated superoxide concentrations in hairy roots overexpressing PvRbohB, determined the status of early and late events of both Rhizobium and AMF interactions in symbiont‐inoculated roots, and analyzed the nodule ultrastructure of transgenic plants overexpressing PvRbohB. Overexpression of PvRbohB significantly enhanced ROS production, the formation of ITs, nodule biomass, and nitrogen‐fixing activity, and increased the density of symbiosomes in nodules, and the density and size of bacteroides in symbiosomes. Furthermore, PvCAT, early nodulin, PvSS1, and PvGOGAT transcript abundances were elevated in these nodules. By contrast, mycorrhizal colonization was reduced in roots that overexpressed RbohB. Overexpression of PvRbohB augmented nodule efficiency by enhancing nitrogen fixation and delaying nodule senescence, but impaired AMF colonization.

Plant immune systems rely on pattern recognition receptors (PRRs) to specifically detect diverse pathogen/pest-associated molecular patterns (PAMPs). While many distinct receptors are known to mediate PAMP recognition, the role of transcriptional regulation of PRRs remains poorly understood. In legume plants, Inceptin Receptor (INR) senses an 11-amino acid peptide, In11, to activate direct and indirect defenses against caterpillar pests. Here we investigated the genetic basis of the rare In11 insensitivity phenotype found in common bean ( Phaseolus vulgaris ) landraces. Natural variation in the rapid In11-induced ethylene response corresponded with genetic variation at the locus encoding INR itself. Surprisingly, phenotypic variation corresponded with expression level of INR , rather than coding sequence variation. Promoter sequence variation across 21 accessions of Andean Phaseolus vulgaris from northwestern Argentina, as well as near-isogenic lines (NILs) derived from crosses between an In11-sensitive and insensitive line, corresponded with strength of In11-induced ethylene response. Promoter alleles also corresponded with strength of activation of a luciferase reporter in the heterologous expression model, Nicotiana benthamiana, indicating that cis-element variation is sufficient to drive differences in leaf expression levels. Surprisingly, NILs encoding either WT INR or the lower expression inr-2 allele did not show differences in resistance to herbivory by beet armyworm ( Spodoptera exigua ), or in In11-pretreatment protection assays, suggesting that even low INR expression can still mediate effective responses against herbivores despite insensitivity to the In11 elicitor in laboratory assays. Our results demonstrate that natural variation in PRR expression can contribute to differential PAMP responses while not necessarily affecting downstream resistance phenotypes.

Premise of the study: The soil-inhabiting insect-pathogenic fungus Metarhizium robertsii also colonizes plant roots endophytically, thus showing potential as a plant symbiont. Metarhizium robertsii is not randomly distributed in soils but preferentially associates with the plant rhizosphere when applied in agricultural settings. Root surface and endophytic colonization of switchgrass (Panicum virgatum) and haricot beans (Phaseolus vulgaris) by M. robertsii were examined after inoculation with fungal conidia. Methods: We used light and confocal microscopy to ascertain the plant endophytic association with GFP-expressing M. robertsii. Root lengths, root hair density, and lateral roots emerged were also observed. Key results: Initially, M. robertsii conidia adhered to, germinated on, and colonized roots. Furthermore, plant roots treated with Metarhizium grew faster and the density of plant root hairs increased when compared with control plants. The onset of plant root hair proliferation was initiated before germination of M. robertsii on the root (within 1-2 d). Plants inoculated with M.robertsii AMAD2 (plant adhesin gene) took significantly longer to show root hair proliferation than the wild type. Cell free extracts of M. robertsii did not stimulate root hair proliferation. Longer-term (60 d) associations showed that M. robertsii endophytically colonized cortical cells within bean roots. Metarhizium appeared as a mycelial aggregate within root cortical cells as well as between the intercellular spaces with no apparent damage to the plant. Conclusions: These results suggest that M. robertsii is not only rhizosphere competent but also displays a beneficial endophytic association with plant roots that results in the proliferation of root hairs.

The cultivation of common beans ( Phaseolus vulgaris L.) in semi-arid regions is affected by drought. To explore potential alleviation strategies, we investigated the impact of inoculation with Bacillus velezensis , and the application of acetylsalicylic acid (ASA) via foliage application (FA), which promote plant growth and enhance stress tolerance. A split-split-plot experiment with four replications was conducted, featuring two irrigation levels: full watering (FW, 100% of plant water requirements) and deficit watering (DW, 70% of plant water requirements) as a main plot, two ASA levels (No foliage application (NFA) 0 and 0.5 mM) as sub plot, and bacterial inoculation (BI) versus non-bacterial inoculation (NBI) as sub-sub plot. Results showed that the highest grain yield was achieved with the ASA + BI under FW (3270 kg ha − ¹), a 56% increase compared to the control (2094 kg ha − ¹). Under DW, the ASA + BI increased yield by approximately 30%. ASA significantly increased relative water content under deficit watering, achieving 84% with BI. Chlorophyll a content peaked at 3.11 mg g − 1 with full watering, and chlorophyll b content increased by up to 23.8% under deficit watering, indicating improved photosynthetic capacity. Malondialdehyde and hydrogen peroxide levels were reduced to 10.88 and 14.81 µmol g − ¹ fresh weight, respectively, in ASA + BI treatments, demonstrating reduced oxidative stress. Antioxidant enzyme activities were significantly elevated in treated plants under DW. This study demonstrates the potential of microbial and hormonal treatments in boosting drought tolerance in common beans, providing a viable approach for sustaining crop performance under stress conditions.

The use of agricultural fertilizers is one of the methods to beat the desired enormous increase in universal food production. The application of nanotechnology in agriculture is regarded as one of the promising approaches to elevate crop production. Whereas mineral nutrients play a crucial role in the growth and yield of the common bean. The experiments were conducted to investigate the application effect of micronutrients as nanoparticles (MN-NPs) on the common ben plants. The trial was performed in the field in El-Menofya, Egypt, through two seasons (2019 & 2020) in a randomized complete block design with three replicates and four combinations of MN-NPs (ZnO, MnO 2 and MoO 3 ) with concentrations 0, 10, 20, 30, 40 mg/L as a foliar application. The data exhibited that the foliar application of MN-NPs significantly upgraded the vegetative growth characters, flower number/plant, photosynthetic pigments, and yield. The concentration of 40 mg/L of MN-NPs leads to improving the vegetative growth, flowering number, and yield characteristics of the common bean. While the biochemical components varied in their response to MN-NPs combinations. The recommended MN-NPs concentration to ameliorate the common bean growth and yield was 40 mg/L.

Background Physical seed dormancy is an important trait in legume domestication. Although seed dormancy is beneficial in wild ecosystems, it is generally considered to be an undesirable trait in crops due to reduction in yield and / or quality. The physiological mechanism and underlying genetic factor(s) of seed dormancy is largely unknown in several legume species. Here we employed an integrative approach to understand the mechanisms controlling physical seed dormancy in common bean ( Phaseolus vulgaris L.). Results Using an innovative CT scan imaging system, we were able to track water movements inside the seed coat. We found that water uptake initiates from the bean seed lens. Using a scanning electron microscopy (SEM) we further identified several micro-cracks on the lens surface of non-dormant bean genotypes. Bulked segregant analysis (BSA) was conducted on a bi-parental RIL (recombinant inbred line) population, segregating for seed dormancy. This analysis revealed that the seed water uptake is associated with a single major QTL on Pv03. The QTL region was fine-mapped to a 118 Kb interval possessing 11 genes. Coding sequence analysis of candidate genes revealed a 5-bp insertion in an ortholog of pectin acetylesterase 8 that causes a frame shift, loss-of-function mutation in non-dormant genotype. Gene expression analysis of the candidate genes in the seed coat of contrasting genotypes indicated 21-fold lower expression of pectin acetylesterase 8 in non-dormant genotype. An analysis of mutational polymorphism was conducted among wild and domesticated beans. Although all the wild beans possessed the functional allele of pectin acetylesterase 8 , the majority (77%) of domesticated beans had the non-functional allele suggesting that this variant was under strong selection pressure through domestication. Conclusions In this study, we identified the physiological mechanism of physical seed dormancy and have identified a candidate allele causing variation in this trait. Our findings suggest that a 5-bp insertion in an ortholog of pectin acetylesterase 8 is likely a major causative mutation underlying the loss of seed dormancy during domestication. Although the results of current study provide strong evidences for the role of pectin acetylesterase 8 in seed dormancy, further confirmations seem necessary by employing transgenic approaches.

Background Xanthomonas citri pv. fuscans (Xcf) and Xanthomonas phaseoli pv. phaseoli (Xpp) are the causal agents of common bacterial blight of bean (CBB), an important disease worldwide that remains difficult to control. These pathogens belong to distinct species within the Xanthomonas genus and have undergone a dynamic evolutionary history including the horizontal transfer of genes encoding factors probably involved in adaptation to and pathogenicity on common bean. Seed transmission is a key point of the CBB disease cycle, favouring both vertical transmission of the pathogen and worldwide distribution of the disease through global seed trade. Taxonomy Kingdom: Bacteria; phylum: Proteobacteria; class: Gammaproteobacteria; order: Lysobacterales (also known as Xanthomonadales); family: Lysobacteraceae (also known as Xanthomonadaceae); genus: Xanthomonas; species: X. citri pv. fuscans and X. phaseoli pv. phaseoli (Xcf‐Xpp). Host range The main host of Xcf‐Xpp is the common bean (Phaseolus vulgaris). Lima bean (Phaseolus lunatus) and members of the Vigna genus (Vigna aconitifolia, Vigna angularis, Vigna mungo, Vigna radiata, and Vigna umbellata) are also natural hosts of Xcf‐Xpp. Natural occurrence of Xcf‐Xpp has been reported for a handful of other legumes such as Calopogonium sp., Pueraria sp., pea (Pisum sativum), Lablab purpureus, Macroptilium lathyroides, and Strophostyles helvola. There are conflicting reports concerning the natural occurrence of CBB agents on tepary bean (Phaseolus acutifolius) and cowpea (Vigna unguiculata subsp. unguiculata). Symptoms CBB symptoms occur on all aerial parts of beans, that is, seedlings, leaves, stems, pods, and seeds. Symptoms initially appear as water‐soaked spots evolving into necrosis on leaves, pustules on pods, and cankers on twigs. In severe infections, defoliation and wilting may occur. Distribution CBB is distributed worldwide, meaning that it is frequently encountered in most places where bean is cultivated in the Americas, Asia, Africa, and Oceania, except for arid tropical areas. Xcf‐Xpp are regulated nonquarantine pathogens in Europe and are listed in the A2 list by the European and Mediterranean Plant Protection Organization (EPPO). Genome The genome consists of a single circular chromosome plus one to four extrachromosomal plasmids of various sizes, for a total mean size of 5.27 Mb with 64.7% GC content and an average predicted number of 4,181 coding sequences. Disease control Management of CBB is based on integrated approaches that comprise measures aimed at avoiding Xcf‐Xpp introduction through infected seeds, cultural practices to limit Xcf‐Xpp survival between host crops, whenever possible the use of tolerant or resistant bean genotypes, and chemical treatments, mainly restricted to copper compounds. The use of pathogen‐free seeds is essential in an effective management strategy and requires appropriate sampling, detection, and identification methods. Useful websites https://gd.eppo.int/taxon/XANTPH, https://gd.eppo.int/taxon/XANTFF, and http://www.cost.eu/COST_Actions/ca/CA16107. This pathogen profile summarizes the current knowledge on Xanthomonas phaseoli pv. phaseoli and Xanthomonas citri pv. fuscans, two phylogenetically distant groups of strains that cause common bacterial blight of bean. ​

Shallow basal root growth angle (BRGA) increases phosphorus acquisition efficiency by enhancing topsoil foraging because in most soils, phosphorus is concentrated in the topsoil. Root hair length and density (RHL/D) increase phosphorus acquisition by expanding the soil volume subject to phosphorus depletion through diffusion. We hypothesized that shallow BRGA and large RHL/D are synergetic for phosphorus acquisition, meaning that their combined effect is greater than the sum of their individual effects. To evaluate this hypothesis, phosphorus acquisition in the field in Mozambique was compared among recombinant inbred lines of common bean (Phaseolus vulgaris) having four distinct root phenotypes: long root hairs and shallow basal roots, long root hairs and deep basal roots, short root hairs and shallow basal roots, and short root hairs and deep basal roots. The results revealed substantial synergism between BRGA and RHL/D. Compared with short-haired, deep-rooted phenotypes, long root hairs increased shoot biomass under phosphorus stress by 89%, while shallow roots increased shoot biomass by 58%. Genotypes with both long root hairs and shallow roots had 298%greater biomass accumulation than short-haired, deep-rooted phenotypes. Therefore, the utility of shallow basal roots and long root hairs for phosphorus acquisition in combination is twice as large as their additive effects.We conclude that the anatomical phene of long, dense root hairs and the architectural phene of shallower basal root growth are synergetic for phosphorus acquisition. Phene synergism may be common in plant biology and can have substantial importance for plant fitness, as shown here.