SPIRE-a software tool for bicontinuous phase recognition: application for plastid cubic membranes.

Bicontinuous membranes in cell organelles epitomize nature's ability to create complex functional nanostructures. Like their synthetic counterparts, these membranes are characterized by continuous membrane sheets draped onto topologically complex saddle-shaped surfaces with a periodic network-like structure. Their structure sizes, (around 50-500 nm), and fluid nature make transmission electron microscopy (TEM) the analysis method of choice to decipher their nanostructural features. Here we present a tool, Surface Projection Image Recognition Environment (SPIRE), to identify bicontinuous structures from TEM sections through interactive identification by comparison to mathematical "nodal surface" models. The prolamellar body (PLB) of plant etioplasts is a bicontinuous membrane structure with a key physiological role in chloroplast biogenesis. However, the determination of its spatial structural features has been held back by the lack of tools enabling the identification and quantitative analysis of symmetric membrane conformations. Using our SPIRE tool, we achieved a robust identification of the bicontinuous diamond surface as the dominant PLB geometry in angiosperm etioplasts in contrast to earlier long-standing assertions in the literature. Our data also provide insights into membrane storage capacities of PLBs with different volume proportions and hint at the limited role of a plastid ribosome localization directly inside the PLB grid for its proper functioning. This represents an important step in understanding their as yet elusive structure-function relationship.

Growth analysis, photosynthate partition and nodulation in bean and soybean / Análise de crescimento, partição de fotoassimilados e nodulação em feijão e soja

Photoassimilate partition and allocation among plant organs varies throughout their development and is also influenced by factors inherent to the genotype and the environment. Nodulation in the soybean-diazotrophic bacteria interaction is more effective than in the bean-diazotrophic bacteria interaction. This investigation studied growth and photoassimilate partitioning throughout the bean and soybean cycles and inferred how much it could affect the nodulation of the roots. For this purpose, an experiment with two treatments was carried out, soybean (cultivar BRS GO - 7760 - RR) and bean (cultivar BRS Estilo), with four replications, conducted in pots and entirely randomized. The seeds were inoculated with commercial rhizobia specific for bean and soybean LeguMax® (Novozymes-Turfal). Plants were analyzed throughout their cycles based on leaf area and dry mass of all organs, including nodules. Mathematical models were fitted to the data and based on them, the instantaneous physiological indicators of growth were estimated, and the percentages of photoassimilate partition among organs were evaluated. Crop growth rate, relative growth rates, net assimilation rate as well as net photosynthesis rate had higher values in soybean compared to bean, following the pattern of leaf area and total dry mass. For both species, the highest rates occurred at the beginning of the cycle, decreasing with age. Unlike the bean, soybean has a high capacity to supply photosynthates to all of its organs throughout its entire cycle, favoring the maintenance of nodule growth and explaining its greater capacity for nitrogen assimilation.

Durante o desenvolvimento das plantas a partição e alocação de fotoassimilados variam entre os seus órgãos, e dependem de fatores inerentes ao genótipo e ao meio ambiente. A nodulação é mais efetiva na interação soja-bactéria diazotrófica do que na interação feijão-bactéria diazotrófica. Esta pesquisa tem como objetivo estudar o crescimento e a partição de fotoassimilados ao longo dos ciclos do feijão e da soja e inferir o quanto isso pode afetar a nodulação das raízes. Para tanto, foi instalado um experimento com dois tratamentos, soja (cultivar BRS GO - 7760 - RR) e feijão comum (cultivar BRS Estilo), com quatro repetições, conduzido em vasos e inteiramente ao acaso. As sementes foram inoculadas com inoculantes comerciais específicos para feijão e soja LeguMax® (Novozymes-Turfal). Plantas foram coletadas ao longo de seus ciclos e medidas as áreas foliares e as massas secas de todos os órgãos, incluindo nódulos. Modelos matemáticos foram ajustados aos dados e, com base neles, foram estimados os indicadores fisiológicos instantâneos do crescimento e, também, foram avaliadas as porcentagens de partição de fotoassimilados entre os órgãos. A taxa de crescimento das culturas (CGR), as taxas de crescimento relativo (RGR), a taxa líquida de assimilação (NAR) e a taxa líquida de fotossíntese (Pn) apresentaram maiores valores na soja em relação ao feijoeiro. Para ambas as culturas as maiores taxas ocorreram no início do ciclo, decrescendo ao longo do ciclo cultural. Diferentemente do feijoeiro a soja tem alta capacidade de suprir de fotoassimilados a todos os seus órgãos ao longo de todo o seu ciclo, o que favorece o maior crescimento dos seus nódulos, justificando a sua maior capacidade na captura do N2 atmosférico.

Bean and Pea Plastoglobules Change in Response to Chilling Stress.

Plastoglobules (PGs) might be characterised as microdomains of the thylakoid membrane that serve as a platform to recruit proteins and metabolites in their spatial proximity in order to facilitate metabolic channelling or signal transduction. This study provides new insight into changes in PGs isolated from two plant species with different responses to chilling stress, namely chilling-tolerant pea (Pisum sativum) and chilling-sensitive bean (Phaseolus coccineus). Using multiple analytical methods, such as high-performance liquid chromatography and visualisation techniques including transmission electron microscopy and atomic force microscopy, we determined changes in PGs' biochemical and biophysical characteristics as a function of chilling stress. Some of the observed alterations occurred in both studied plant species, such as increased particle size and plastoquinone-9 content, while others were more typical of a particular type of response to chilling stress. Additionally, PGs of first green leaves were examined to highlight differences at this stage of development. Observed changes appear to be a dynamic response to the demands of photosynthetic membranes under stress conditions.

Assessing the effects of a novel biostimulant to enhance leafminer resistance and plant growth on common bean.

The leafminer Liriomyza trifolii is one of the major insects that affect Phaseolus vulgaris production worldwide. Novel and safe biobased stimulator compound (BSTC) with micronutrient-amino acid chelated compounds was developed from natural compounds and was used for foliar spray of P. vulgaris. Treated plants showed significantly increased in quality and productivity as well as significant reduction in leafminer infestation by close the tunnel end resulting in larvae suffocation and death. BSTC contains chemical composition that has important function in inducing immunity and resistance against insects, enhance plant growth and production. Also, HPLC showed that the assembled BSTC is rich in nucleobases than yeast extract (> 56 fold). Aminochelation zinc enhanced the rate of absorption of nutrient compounds and could participate in safe biofortification strategy. The expression of plant defense related genes under BSTC treatment revealed strong correlations between the transcription rates of defense related genes. Based on binding energies and interacting residues of six vital insect proteins, the best-docked complexes was obtained with disodium 5'-inosinate, delphinidin 3-glucoside and hyperoside. Obtained findings indicate that the foliar application of BSTC can enhance plant growth and productivity, uptake of important elements, expression of defense related genes and inhibit insect essential genes.

Morphological, Biochemical, and Proteomic Studies Revealed Impact of Fe and P Crosstalk on Root Development in Phaseolus vulgaris L.

Mineral stress is one of the major abiotic stresses faced by crop plants. The present study was undertaken to investigate the impact of mineral stress (iron (Fe) and phosphorus (P)) on various morphological and biochemical responses of the shoot and root tissues and root architecture of common bean (Phaseolus vulgaris L.). This study also leads us to the identification of P stress responsive proteins. The study was conducted under in vitro conditions, in which seeds of Shalimar French Bean-1 (SFB-1) variety were cultured on four different MGRL medium (control (P1Fe1), iron deficient (P1Fe0), phosphorus deficient (P0Fe1), and phosphorus and iron deficient (P0Fe0)). Chlorophyll content of leaves, Fe/P content of root tissues, total sugars, proline, length, and weight of shoot and root tissues were assessed and compared within and between the treatments. The analyzed data revealed significant difference between control and other three treatments. Chlorophyll content of shoots was found significantly decreased under mineral stress treatments P0Fe1, P1Fe0, and P0Fe0 than control. Length and weight of shoot and root were also observed significantly decreased under P0Fe1, P1Fe0, and P0Fe0 as compared to control. Total sugar was significantly higher in P0Fe1 of roots in comparison to control. Proline content was significantly higher in both tissues of shoots and roots of plants grown under P1Fe0, P0Fe1, and P0Fe0 than control condition. Furthermore, we unexpectedly observed the recovery of roots (mainly primary roots) under P0Fe0 as compared to P1Fe0 and P0Fe1. Interestingly higher concentration of Fe was also observed in P0Fe1 compared to other treatments and also higher concentration of P was observed in P1Fe1. These findings suggested that there is a crosstalk between Fe and P and also revealed that there is a disruption in the ability of PR (primary root) to sense local P deficiency in the absence of Fe. Furthermore, proteomics analysis (SDS-PAGE followed by MALDI MS) helped in identification of defensive proteins in P stress condition compared to control.

Germination of Phaseolus vulgaris L. Seeds after a Short Treatment with a Powerful RF Plasma.

Seeds of common bean (Phaseolus vulgaris L.), of the Etna variety, were treated with low-pressure oxygen plasma sustained by an inductively coupled radiofrequency discharge in the H-mode for a few seconds. The high-intensity treatment improved seed health in regard to fungal contamination. Additionally, it increased the wettability of the bean seeds by altering surface chemistry, as established by X-ray photoelectron spectroscopy, and increasing surface roughness, as seen with a scanning electron microscope. The water contact angle at the seed surface dropped to immeasurably low values after a second of plasma treatment. Hydrophobic recovery within a month returned those values to no more than half of the original water contact angle, even for beans treated for the shortest time (0.5 s). Increased wettability resulted in accelerated water uptake. The treatment increased the bean radicle length, which is useful for seedling establishment in the field. These findings confirm that even a brief plasma treatment is a useful technique for the disinfection and stimulation of radicle growth. The technique is scalable to large systems due to the short treatment times.

Seed priming with endophytic Bacillus subtilis strain-specifically improves growth of Phaseolus vulgaris plants under normal and salinity conditions and exerts anti-stress effect through induced lignin deposition in roots and decreased oxidative and osmotic damages.

Bacillus subtilis is one of the non-pathogenic beneficial bacteria that promote plant growth and stress tolerance. In the present study, we revealed that seed priming with endophytic B. subtilis (strains 10-4, 26D) improved Phaseolus vulgaris L. (common bean) seed germination and plant growth under both saline and non-saline conditions. 10-4 and 26D decreased oxidative and osmotic damage to the plant cells since bacterial inoculations reduced lipid peroxidation and proline accumulation in plants under salinity. 26D and especially 10-4 preserved different elevated levels of chlorophyll (Chl) a and Chl b in bean leaves under salinity, while carotenoids (Car) increased only by 10-4 and slightly decreased by 26D. Under normal conditions, 10-4 and 26D did not affect Chl a and Car concentrations, while Chl b decreased in the same plants. Under non-saline and especially saline conditions, 10-4 and 26D significantly increased lignin accumulation in plant roots and the highest lignin content along with better growth and oxidative damages reduction was observed after 10-4 inoculation under salinity, indicating a major role of B. subtilis-induced strengthening the root cell walls in the implementation protective effect of studied bacteria on plants. Therefore, B. subtilis 10-4 and 26D exerts protective effects on the growth of common bean plants under salinity by regulating plant defense mechanisms and the major role in tolerance development may contribute through the activation by B. subtilis lignin deposition in roots. The obtained data also indicates a strain-dependent efficiency of endophytic B. subtilis since strains 10-4 and 26D differently improved growth attributes and modulates cellular response reactions of the same common bean plants both under normal and salinity conditions, that generates interest for further investigations in this direction.

Genome-wide association mapping reveals new loci associated with light-colored seed coat at harvest and slow darkening in carioca beans.

BACKGROUND: Common bean (Phaseolus vulgaris L.) is a legume whose grain can be stored for months, a common practice among Brazilian growers. Over time, seed coats become darker and harder to cook, traits that are undesirable to consumers, who associate darker-colored beans with greater age. Like commercial pinto and cranberry bean varieties, carioca beans that have darker seeds at harvest time and after storage are subject to decreased market values. RESULTS: The goal of our study was to identify the genetic control associated with lightness of seed coat color at harvest (HL) and with tolerance to post-harvest seed coat darkening (PHD) by a genome-wide association study. For that purpose, a carioca diversity panel previously validated for association mapping studies was used with 138 genotypes and 1,516 high-quality SNPs. The panel was evaluated in two environments using a colorimeter and the CIELAB scale. Shelf storage for 30 days had the most expressive results and the L* (luminosity) parameter led to the greatest discrimination of genotypes. Three QTL were identified for HL, two on chromosome Pv04 and one on Pv10. Regarding PHD, results showed that genetic control differs for L* after 30 days and for the ΔL* (final L*-initial L*); only ΔL* was able to properly express the PHD trait. Four phenotypic classes were proposed, and five QTL were identified through six significant SNPs. CONCLUSIONS: Lightness of seed coat color at harvest showed an oligogenic inheritance corroborated by moderate broad-sense heritability and high genotypic correlation among the experiments. Only three QTL were significant for this trait - two were mapped on Pv04 and one on Pv10. Considering the ΔL, six QTL were mapped on four different chromosomes for PHD. The same HL QTL at the beginning of Pv10 was also associated with ΔL* and could be used as a tool in marker-assisted selection. Several candidate genes were identified and may be useful to accelerate the genetic breeding process.

Beneficial insects are associated with botanically rich margins with trees on small farms.

Beneficial insect communities on farms are influenced by site- and landscape-level factors, with pollinator and natural enemy populations often associated with semi-natural habitat remnants. They provide ecosystem services essential for all agroecosystems. For smallholders, natural pest regulation may be the only affordable and available option to manage pests. We evaluated the beneficial insect community on smallholder bean farms (Phaseolus vulgaris L.) and its relationship with the plant communities in field margins, including margin trees that are not associated with forest fragments. Using traps, botanical surveys and transect walks, we analysed the relationship between the floral diversity/composition of naturally regenerating field margins, and the beneficial insect abundance/diversity on smallholder farms, and the relationship with crop yield. More flower visits by potential pollinators and increased natural enemy abundance measures in fields with higher plant, and particularly tree, species richness, and these fields also saw improved crop yields. Many of the flower visitors to beans and potential natural enemy guilds also made use of non-crop plants, including pesticidal and medicinal plant species. Selective encouragement of plants delivering multiple benefits to farms can contribute to an ecological intensification approach. However, caution must be employed, as many plants in these systems are introduced species.

Genetic Diversity and Characterization of Symbiotic Bacteria Isolated from Endemic Phaseolus Cultivars Located in Contrasting Agroecosystems in Venezuela.

Phaseolus vulgaris is a grain cultivated in vast areas of different countries. It is an excellent alternative to the other legumes in the Venezuelan diet and is of great agronomic interest due to its resistance to soil acidity, drought, and high temperatures. Phaseolus establishes symbiosis primarily with Rhizobium and Ensifer species in most countries, and this rhizobia-legume interaction has been studied in Asia, Africa, and the Americas. However, there is currently no evidence to show that rhizobia nodulate the endemic cultivars of P. vulgaris in Venezuela. Therefore, we herein investigated the phylogenetic diversity of plant growth-promoting and N2-fixing nodulating bacteria isolated from the root nodules of P. vulgaris cultivars in a different agroecosystem in Venezuela. In comparisons with other countries, higher diversity was found in isolates from P. vulgaris nodules, ranging from α- and ß-proteobacteria. Some isolates belonging to several new phylogenetic lineages within Bradyrhizobium, Ensifer, and Mesorhizobium species were also specifically isolated at some topographical regions. Additionally, some isolates exhibited tolerance to high temperature, acidity, alkaline pH, salinity stress, and high Al levels; some of these characteristics may be related to the origin of the isolates. Some isolates showed high tolerance to Al toxicity as well as strong plant growth-promoting and antifungal activities, thereby providing a promising agricultural resource for inoculating crops.

A methyl esterase 1 (PvMES1) promotes the salicylic acid pathway and enhances Fusarium wilt resistance in common beans.

KEY MESSAGE: Methyl esterase (MES), PvMES1, contributes to the defense response toward Fusarium wilt in common beans by regulating the salicylic acid (SA) mediated signaling pathway from phenylpropanoid synthesis and sugar metabolism as well as others. Common bean (Phaseolus vulgaris L.) is an important food legume. Fusarium wilt caused by Fusarium oxysporum f. sp. phaseoli is one of the most serious soil-borne diseases of common bean found throughout the world and affects the yield and quality of the crop. Few sources of Fusarium wilt resistance exist in legumes and most are of quantitative inheritance. In this study, we have identified a methyl esterase (MES), PvMES1, that contributes to plant defense response by regulating the salicylic acid (SA) mediated signaling pathway in response to Fusarium wilt in common beans. The result showed the role of PvMES1 in regulating SA levels in common bean and thus the SA signaling pathway and defense response mechanism in the plant. Overexpression of the PvMES1 gene enhanced Fusarium wilt resistance; while silencing of the gene caused susceptibility to the diseases. RNA-seq analysis with these transiently modified plants showed that genes related to SA level changes included the following gene ontologies: (a) phenylpropanoid synthesis; (b) sugar metabolism; and (c) interaction between host and pathogen as well as others. These key signal elements activated the defense response pathway in common bean to Fusarium wilt. Collectively, our findings indicate that PvMES1 plays a pivotal role in regulating SA biosynthesis and signaling, and increasing Fusarium wilt resistance in common bean, thus providing novel insight into the practical applications of both SA and MES genes and pathways they contribute to for developing elite crop varieties with enhanced broad-spectrum resistance to this critical disease.

Comparative Study between Exogenously Applied Plant Growth Hormones versus Metabolites of Microbial Endophytes as Plant Growth-Promoting for Phaseolus vulgaris L.

Microbial endophytes organize symbiotic relationships with the host plant, and their excretions contain diverse plant beneficial matter such as phytohormones and bioactive compounds. In the present investigation, six bacterial and four fungal strains were isolated from the common bean (Phaseolus vulgaris L.) root plant, identified using molecular techniques, and their growth-promoting properties were reviewed. All microbial isolates showed varying activities to produce indole-3-acetic acid (IAA) and different hydrolytic enzymes such as amylase, cellulase, protease, pectinase, and xylanase. Six bacterial endophytic isolates displayed phosphate-solubilizing capacity and ammonia production. We conducted a field experiment to evaluate the promotion activity of the metabolites of the most potent endophytic bacterial (Bacillus thuringiensis PB2 and Brevibacillus agri PB5) and fungal (Alternaria sorghi PF2 and, Penicillium commune PF3) strains in comparison to two exogenously applied hormone, IAA, and benzyl adenine (BA), on the growth and biochemical characteristics of the P. vulgaris L. Interestingly, our investigations showed that bacterial and fungal endophytic metabolites surpassed the exogenously applied hormones in increasing the plant biomass, photosynthetic pigments, carbohydrate and protein contents, antioxidant enzyme activity, endogenous hormones and yield traits. Our findings illustrate that the endophyte Brevibacillus agri (PB5) provides high potential as a stimulator for the growth and productivity of common bean plants.

Evaluation of Chalcone Derivatives as Photosynthesis and Plant Growth Inhibitors.

We report the evaluation of chalcone derivatives as photosystem II (PSII) and plant growth inhibitors. Chalcone derivatives were evaluated as PSII inhibitors through Chl a fluorescence measurement. (E)-Chalcone (6a) and (E)-3-(4-bromophenyl)-1-(4-fluorophenyl)prop-2-en-1-one (6j) showed the best results, reducing the performance index on absorption basis parameter (PIabs ) by 70 %. Additionally, the decrease of TR0 /RC and ET0 /RC parameters indicates that the chalcone derivatives limited the number of active PSII reaction centers and the amount of trapped energy within them. Compounds 6a and 6j both act as post-emergent herbicides at 50 µM, reducing the root biomass of the Ipomoea grandifolia weed by 72 % and 83 %, respectively, corroborating the fluorescence results. The selectivity against weeds as compared to valuable crops by compounds 6a and 6j were evaluated employing Zea mays and Phaseolus vulgaris plants. In these, our newly synthesized compounds showed no effects on biomass accumulation of roots and aerial parts when compared to the control, providing valuable evidence for the role of these compounds as selective inhibitors of the growth of undesired weeds.

Genome-wide association study for grain mineral content in a Brazilian common bean diversity panel.

KEY MESSAGE: QTNs significantly associated to nine mineral content in grains of common bean were identified. The accumulation of favorable alleles was associated with a gradually increasing nutrient content in the grain. Biofortification is one of the strategies developed to address malnutrition in developing countries, the aim of which is to improve the nutritional content of crops. The common bean (Phaseolus vulgaris L.), a staple food in several African and Latin American countries, has excellent nutritional attributes and is considered a strong candidate for biofortification. The objective of this study was to identify genomic regions associated with nutritional content in common bean grains using 178 Mesoamerican accessions belonging to a Brazilian Diversity Panel (BDP) and 25,011 good-quality single nucleotide polymorphisms. The BDP was phenotyped in three environments for nine nutrients (phosphorus, potassium, calcium, magnesium, copper, manganese, sulfur, zinc, and iron) using four genome-wide association multi-locus methods. To obtain more accurate results, only quantitative trait nucleotides (QTNs) that showed repeatability (i.e., those detected at least twice using different methods or environments) were considered. Forty-eight QTNs detected for the nine minerals showed repeatability and were considered reliable. Pleiotropic QTNs and overlapping genomic regions surrounding the QTNs were identified, demonstrating the possible association between the deposition mechanisms of different nutrients in grains. The accumulation of favorable alleles in the same accession was associated with a gradually increasing nutrient content in the grain. The BDP proved to be a valuable source for association studies. The investigation of different methods and environments showed the reliability of markers associated with minerals. The loci identified in this study will potentially contribute to the improvement of Mesoamerican common beans, particularly carioca and black beans, the main groups consumed in Brazil.

Morpho-agronomic, biochemical and molecular analysis of genetic diversity in the Mesoamerican common bean panel.

The common bean (Phaseolus vulgaris L.) is of great importance to the food and nutritional security of many populations, and exploitation of the crop's genetic diversity is essential for the success of breeding programs. Thus, the aim of the present study was to evaluate the genetic diversity of 215 common bean accessions, which included cultivars, obsolete cultivars, improved lines, and landraces using morpho-agronomic and biochemical traits, and amplified fragment length polymorphism markers (AFLP). Genetic parameters, box plots, Pearson's correlation analysis, and Ward's hierarchical clustering were used to analyze the data. The Jaccard similarity coefficient and neighbour-joining clustering method were used for molecular analysis. A wide variability among the accessions was observed for morpho-agronomic and biochemical traits. Selective accuracy (Ac) and broad-sense heritability (h2) values were high to intermediate for all traits, except seed yield. Ward's hierarchical clustering analysis generated six groups. AFLP analysis also revealed significant differences among the accessions. There was no correlation between the differences based on genetic markers and those based on morpho-agronomic and biochemical data, which indicates that both datasets are important for elucidating the differences among accessions. The results of the present study indicate great genetic diversity among the evaluated accessions.

Allelic Diversity at Abiotic Stress Responsive Genes in Relationship to Ecological Drought Indices for Cultivated Tepary Bean, Phaseolus acutifolius A. Gray, and Its Wild Relatives.

Some of the major impacts of climate change are expected in regions where drought stress is already an issue. Grain legumes are generally drought susceptible. However, tepary bean and its wild relatives within Phaseolus acutifolius or P. parvifolius are from arid areas between Mexico and the United States. Therefore, we hypothesize that these bean accessions have diversity signals indicative of adaptation to drought at key candidate genes such as: Asr2, Dreb2B, and ERECTA. By sequencing alleles of these genes and comparing to estimates of drought tolerance indices from climate data for the collection site of geo-referenced, tepary bean accessions, we determined the genotype x environmental association (GEA) of each gene. Diversity analysis found that cultivated and wild P. acutifolius were intermingled with var. tenuifolius and P. parvifolius, signifying that allele diversity was ample in the wild and cultivated clade over a broad sense (sensu lato) evaluation. Genes Dreb2B and ERECTA harbored signatures of directional selection, represented by six SNPs correlated with the environmental drought indices. This suggests that wild tepary bean is a reservoir of novel alleles at genes for drought tolerance, as expected for a species that originated in arid environments. Our study corroborated that candidate gene approach was effective for marker validation across a broad genetic base of wild tepary accessions.

Physiological and genetic characterization of heat stress effects in a common bean RIL population.

Heat stress is a major abiotic stress factor reducing crop productivity and climate change models predict increasing temperatures in many production regions. Common bean (Phaseolus vulgaris L.) is an important crop for food security in the tropics and heat stress is expected to cause increasing yield losses. To study physiological responses and to characterize the genetics of heat stress tolerance, we evaluated the recombinant inbred line (RIL) population IJR (Indeterminate Jamaica Red) x AFR298 of the Andean gene pool. Heat stress (HS) conditions in the field affected many traits across the reproductive phase. High nighttime temperatures appeared to have larger effects than maximum daytime temperatures. Yield was reduced compared to non-stress conditions by 37% and 26% in 2016 and 2017 seasons, respectively. The image analysis tool HYRBEAN was developed to evaluate pollen viability (PolVia). A significant reduction of PolVia was observed in HS and higher viability was correlated with yield only under stress conditions. In susceptible lines the reproductive phase was extended and defects in the initiation of seed, seed fill and seed formation were identified reducing grain quality. Higher yields under HS were correlated with early flowering, high pollen viability and effective seed filling. Quantitative trait loci (QTL) analysis revealed a QTL for both pod harvest index and PolVia on chromosome Pv05, for which the more heat tolerant parent IJR contributed the positive allele. Also, on chromosome Pv08 a QTL from IJR improved PolVia and the yield component pods per plant. HS affected several traits during the whole reproductive development, from floral induction to grain quality traits, indicating a general heat perception affecting many reproductive processes. Identification of tolerant germplasm, indicator traits for heat tolerance and molecular tools will help to breed heat tolerant varieties to face future climate change effects.

Na+ and/or Cl- Toxicities Determine Salt Sensitivity in Soybean (Glycine max (L.) Merr.), Mungbean (Vigna radiata (L.) R. Wilczek), Cowpea (Vigna unguiculata (L.) Walp.), and Common Bean (Phaseolus vulgaris L.).

Grain legumes are important crops, but they are salt sensitive. This research dissected the responses of four (sub)tropical grain legumes to ionic components (Na+ and/or Cl-) of salt stress. Soybean, mungbean, cowpea, and common bean were subjected to NaCl, Na+ salts (without Cl-), Cl- salts (without Na+), and a "high cation" negative control for 57 days. Growth, leaf gas exchange, and tissue ion concentrations were assessed at different growing stages. For soybean, NaCl and Na+ salts impaired seed dry mass (30% of control), more so than Cl- salts (60% of control). All treatments impaired mungbean growth, with NaCl and Cl- salt treatments affecting seed dry mass the most (2% of control). For cowpea, NaCl had the greatest adverse impact on seed dry mass (20% of control), while Na+ salts and Cl- salts had similar intermediate effects (~45% of control). For common bean, NaCl had the greatest adverse effect on seed dry mass (4% of control), while Na+ salts and Cl- salts impaired seed dry mass to a lesser extent (~45% of control). NaCl and Na+ salts (without Cl-) affected the photosynthesis (Pn) of soybean more than Cl- salts (without Na+) (50% of control), while the reverse was true for mungbean. Na+ salts (without Cl-), Cl- salts (without Na+), and NaCl had similar adverse effects on Pn of cowpea and common bean (~70% of control). In conclusion, salt sensitivity is predominantly determined by Na+ toxicity in soybean, Cl- toxicity in mungbean, and both Na+ and Cl- toxicity in cowpea and common bean.

Biological and molecular characterization of bean bushy stunt virus, a novel bipartite begomovirus infecting common bean in northwestern Argentina.

Common bean plants (Phaseolus vulgaris L.) showing different virus-like symptoms were collected in northwestern Argentina. Dot-blot hybridization tests showed that the begomoviruses bean golden mosaic virus and tomato yellow vein streak virus were the most prevalent, but they also revealed the presence of unknown begomoviruses. The complete genome sequence of one of these unknown begomoviruses was determined. Sequence analysis showed that the virus is a typical New World begomovirus, for which the name "bean bushy stunt virus" (BBSV) is proposed. Biological assays based on biolistic inoculations showed that BBSV induced leaf roll and stunting symptoms similar to those observed in the field-collected common bean sample.

Can low doses of glyphosate stimulate common bean growth?

Plant growth can be stimulated by low doses of glyphosate. The objective of this work was to evaluate the effect of low doses of glyphosate and sowing season on the growth of the early cycle common bean. Two experiments were conducted in the field, the first in the winter and the second in the wet season, with the early cycle common bean cultivar IAC Imperador. The experimental design was a randomized complete block design, consisting of low doses of glyphosate applied on phenological stage V4, with four replications. Environmental conditions, such as air temperature, interfered in the early cycle common bean response to low doses of glyphosate. In the winter season, a dose of 36 g a.e. ha-1 promoted growth in the common bean, and a dose of 7.2 g a.e. ha-1 improved the harvest index. In the wet season, there was no growth stimulus, and the harvest index increased with a dose of 36 g a.e. ha-1. The harvest index was the only characteristic improved in both seasons, but with different doses. Our study indicates that growth characteristics of early cycle common bean are stimulated by low doses of glyphosate, but this response is dependent on the growing environment.