Tepary Research Articles

Exploiting genetic and genomic resources to enhance productivity and abiotic stress adaptation of underutilized pulses.

Underutilized pulses and their wild relatives are typically stress tolerant and their seeds are packed with protein, fibers, minerals, vitamins, and phytochemicals. The consumption of such nutritionally dense legumes together with cereal-based food may promote global food and nutritional security. However, such species are deficient in a few or several desirable domestication traits thereby reducing their agronomic value, requiring further genetic enhancement for developing productive, nutritionally dense, and climate resilient cultivars. This review article considers 13 underutilized pulses and focuses on their germplasm holdings, diversity, crop-wild-crop gene flow, genome sequencing, syntenic relationships, the potential for breeding and transgenic manipulation, and the genetics of agronomic and stress tolerance traits. Recent progress has shown the potential for crop improvement and food security, for example, the genetic basis of stem determinacy and fragrance in moth bean and rice bean, multiple abiotic stress tolerant traits in horse gram and tepary bean, bruchid resistance in lima bean, low neurotoxin in grass pea, and photoperiod induced flowering and anthocyanin accumulation in adzuki bean have been investigated. Advances in introgression breeding to develop elite genetic stocks of grass pea with low β-ODAP (neurotoxin compound), resistance to Mungbean yellow mosaic India virus in black gram using rice bean, and abiotic stress adaptation in common bean, using genes from tepary bean have been carried out. This highlights their potential in wider breeding programs to introduce such traits in locally adapted cultivars. The potential of de-domestication or feralization in the evolution of new variants in these crops are also highlighted.

Multi-Environment Genome-Wide Association Studies of Yield Traits in Common Bean (Phaseolus vulgaris L.) × Tepary Bean (P. acutifolius A. Gray) Interspecific Advanced Lines in Humid and Dry Colombian Caribbean Subregions

Assessing interspecific adaptive genetic variation across environmental gradients offers insight into the scale of habitat-dependent heritable heterotic effects, which may ultimately enable pre-breeding for abiotic stress tolerance and novel climates. However, environmentally dependent allelic effects are often bypassed by intra-specific single-locality genome-wide associations studies (GWAS). Therefore, in order to bridge this gap, this study aimed at coupling an advanced panel of drought/heat susceptible common bean (Phaseolus vulgaris L.) × tolerant tepary bean (P. acutifolius A. Gray) interspecific lines with last-generation multi-environment GWAS algorithms to identify novel sources of heat and drought tolerance to the humid and dry subregions of the Caribbean coast of Colombia, where the common bean typically exhibits maladaptation to extreme weather. A total of 87 advanced lines with interspecific ancestries were genotyped by sequencing (GBS), leading to the discovery of 15,645 single-nucleotide polymorphism (SNP) markers. Five yield traits were recorded for each genotype and inputted in modern GWAS algorithms (i.e., FarmCPU and BLINK) to identify the putative associated loci across four localities in coastal Colombia. Best-fit models revealed 47 significant quantitative trait nucleotides (QTNs) distributed in all 11 common bean chromosomes. A total of 90 flanking candidate genes were identified using 1-kb genomic windows centered in each associated SNP marker. Pathway-enriched analyses were done using the mapped output of the GWAS for each yield trait. Some genes were directly linked to the drought tolerance response; morphological, physiological, and metabolic regulation; signal transduction; and fatty acid and phospholipid metabolism. We conclude that habitat-dependent interspecific polygenic effects are likely sufficient to boost common bean adaptation to the severe climate in coastal Colombia via introgression breeding. Environmental-dependent polygenic adaptation may be due to contrasting levels of selection and the deleterious load across localities. This work offers putative associated loci for marker-assisted and genomic selection targeting the common bean’s neo-tropical lowland adaptation to drought and heat.

Interspecific common bean population derived from Phaseolus acutifolius using a bridging genotype demonstrate useful adaptation to heat tolerance.

Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide and is a major nutrient source in the tropics. Common bean reproductive development is strongly affected by heat stress, particularly overnight temperatures above 20°C. The desert Tepary bean (Phaseolus acutifolius A. Gray) offers a promising source of adaptative genes due to its natural acclimation to arid conditions. Hybridization between both species is challenging, requiring in vitro embryo rescue and multiple backcrossing cycles to restore fertility. This labor-intensive process constrains developing mapping populations necessary for studying heat tolerance. Here we show the development of an interspecific mapping population using a novel technique based on a bridging genotype derived from P. vulgaris, P. Acutifolius and P. parvifolius named VAP1 and is compatible with both common and tepary bean. The population was based on two wild P. acutifolius accessions, repeatedly crossed with Mesoamerican elite common bush bean breeding lines. The population was genotyped through genotyping-by-sequencing and evaluated for heat tolerance by genome-wide association studies. We found that the population harbored 59.8% introgressions from wild tepary, but also genetic regions from Phaseolus parvifolius, a relative represented in some early bridging crosses. We found 27 significative quantitative trait loci, nine located inside tepary introgressed segments exhibiting allelic effects that reduced seed weight, and increased the number of empty pods, seeds per pod, stem production and yield under high temperature conditions. Our results demonstrate that the bridging genotype VAP1 can intercross common bean with tepary bean and positively influence the physiology of derived interspecific lines, which displayed useful variance for heat tolerance.

Traits Related to Heat Stress in Phaseolus Species

Traits related to heat stress in bean species (Phaseolus spp.) have been insufficiently explored to date, yet studies of these traits are needed given that heat stress is predicted to become more frequent and severe in many parts of the world because of climate change. In order to detect agro-morphological and physiological traits related to heat stress and selection for resistance to heat stress, a total of 196 bean genotypes including eight genotypes of tepary bean (P. acutifolius L.), five genotypes of scarlet runner bean (P. coccineus A. Gray), two genotypes of year bean (P. dumosus Macfady), five genotypes of lima bean (P. lunatus L.), and 176 genotypes of common bean (P. vulgaris L.) were evaluated in 2019 and 2020 under moderate (field) and extreme heat stress (greenhouse) conditions. Although most genotypes of P. acutifolius, P. lunatus, and P. coccineus were found to be more resistant to heat stress than most genotypes of common bean, some genotypes of common bean were shown to perform as well as P. acutifolius, P. lunatus, and P. coccineus. Biomass among agronomical traits had the highest significant direct effects on the resistance to heat stress score. The maximum quantum efficiency of PSII and SPAD values among physiological traits showed significant direct effects on the resistance to heat stress score. Biomass, leaflet size, the SPAD value and maximum quantum efficiency of PSII can be considered as heat stress-related traits, and, P. acutifolius, P. lunatus, P. coccineus, and some genotypes of P. vulgaris can be considered for exploitation in a heat stress tolerance breeding program.

Host status and host sensitivity of Kickapoo white tepary bean to Meloidogyne enterolobii

ABSTRACT Tepary bean (Phaseolus acutifolius A. Gray) is a drought tolerant leguminous crop and due to its multi-purpose use, it can easily be incorporated into different production systems. It being an undertilised crop, its production is usually relegated to poor sandy soils that are highly prone to root-knot nematodes (Meloidogyne species). Commonly communal producers of tepary beans use retained seeds with no knowledge of the nematode resistance status of the seeds. Hence the objective of the study was to determine whether Meloidogyne enterolobii will be able to reproduce on the Kickapoo white tepary bean and cause a reduction in the plant's growth variables. To achieve this objective, Kickapoo white tepary bean seedlings were exposed to 0, 25, 50, 125, 250, 625, 1250 and 3125 M. enterolobii eggs and second-stage juveniles (J2) in 2021 and validated in 2022 under shade-net conditions. At 56 days after inoculation, plant and nematode variables were collected and reproductive factor (Rf) was computed. Plant growth variables were not reduced whereas, nematode variables increased with an increase in nematode levels. In both experiments the Rf values were above a unity for all inoculation levels, indicating that nematodes were able to reproduce.. In conclusion, Kickapoo white tepary bean is tolerant to M. enterolobii.

Summer pulses as sources of green manure and soil cover in the U.S. Southern Great Plains

Winter wheat (Triticum aestivum L.) – summer fallow rotations in the Southern Great Plains (SGP) have numerous sustainability issues, such as low precipitation use efficiencies and increased soil erosion. Replacing summer fallow with a legume grown as a green manure would help reduce soil erosion, improve precipitation use efficiency, and add nitrogen (N) credits for the subsequent wheat crop. A two-year field experiment evaluated the capabilities of three summer pulses: soybean [Glycine max (L.) Merr.], moth bean [Vigna aconitifolia (Jacq.) Marechal], and tepary bean [Phaseolus acutifolius (A.) Gray] to serve as green manures and soil cover. We examined their performance across two row spacings (38 and 76 ​cm) and two moisture regimes (rainfed and irrigated). Narrow row spacing (38 ​cm) provided greater canopy cover, aboveground biomass, and N accumulation than the broad row spacing (76 ​cm) during the early growing season. Among species, tepary bean demonstrated consistent and higher canopy cover early in the season. Soybean produced the highest aboveground biomass (5,327–8,855 ​kg ​ha−1) and N accumulation (115–269 ​kg ​ha−1) among the three pulses. Multilinear regression (MLR) models suggested that canopy height and canopy cover could estimate both aboveground biomass (R2 ​= ​0.62) and N accumulation (R2 ​= ​0.55) for tested pulses. Based on results, soybean was the most promising choice among tested pulses, considering its higher aboveground biomass and N accumulation. Modelling studies to simulate growth of these crops with long-term weather scenarios are encouraged to identify the most reliable cover crop for different areas of the SGP.

EGFR and p38MAPK Contribute to the Apoptotic Effect of the Recombinant Lectin from Tepary Bean (Phaseolus acutifolius) in Colon Cancer Cells.

Previous works showed that a Tepary bean lectin fraction (TBLF) induced apoptosis on colon cancer cells and inhibited early colonic tumorigenesis. One Tepary bean (TB) lectin was expressed in Pichia pastoris (rTBL-1), exhibiting similarities to one native lectin, where its molecular structure and in silico recognition of cancer-type N-glycoconjugates were confirmed. This work aimed to determine whether rTBL-1 retained its bioactive properties and if its apoptotic effect was related to EGFR pathways by studying its cytotoxic effect on colon cancer cells. Similar apoptotic effects of rTBL-1 with respect to TBLF were observed for cleaved PARP-1 and caspase 3, and cell cycle G0/G1 arrest and decreased S phase were observed for both treatments. Apoptosis induction on SW-480 cells was confirmed by testing HA2X, p53 phosphorylation, nuclear fragmentation, and apoptotic bodies. rTBL-1 increased EGFR phosphorylation but also its degradation by the lysosomal route. Phospho-p38 increased in a concentration- and time-dependent manner, matching apoptotic markers, and STAT1 showed activation after rTBL-1 treatment. The results show that part of the rTBL-1 mechanism of action is related to p38 MAPK signaling. Future work will focus further on the target molecules of this recombinant lectin against colon cancer.

Hyperspectral Remote Sensing for Phenotyping the Physiological Drought Response of Common and Tepary Bean.

Proximal remote sensing offers a powerful tool for high-throughput phenotyping of plants for assessing stress response. Bean plants, an important legume for human consumption, are often grown in regions with limited rainfall and irrigation and are therefore bred to further enhance drought tolerance. We assessed physiological (stomatal conductance and predawn and midday leaf water potential) and ground- and tower-based hyperspectral remote sensing (400 to 2,400 nm and 400 to 900 nm, respectively) measurements to evaluate drought response in 12 common bean and 4 tepary bean genotypes across 3 field campaigns (1 predrought and 2 post-drought). Hyperspectral data in partial least squares regression models predicted these physiological traits (R 2 = 0.20 to 0.55; root mean square percent error 16% to 31%). Furthermore, ground-based partial least squares regression models successfully ranked genotypic drought responses similar to the physiologically based ranks. This study demonstrates applications of high-resolution hyperspectral remote sensing for predicting plant traits and phenotyping drought response across genotypes for vegetation monitoring and breeding population screening.

Genotype-by-Environment Interaction in Tepary Bean (Phaseolus acutifolius A. Gray) for Seed Yield

Genotype-by-environment (GEI) analysis guides the recommendation of best-performing crop genotypes and production environments. The objective of this study was to determine the extent of GEI on seed yield in tepary bean for genotype recommendation and cultivation in drought-prone environments. Forty-five genetically diverse tepary bean genotypes were evaluated under non-stressed and drought-stressed conditions for two seasons using a 9 × 5 alpha lattice design with three replications in four testing environments. Data were collected on seed yield (SY) and days to physiological maturity (DTM) and computed using a combined analysis of variance, the additive main effect and multiplicative interaction (AMMI), the best linear unbiased predictors (BLUPs), the yield stability index (YSI), the weighted average of absolute scores (WAASB) index, the multi-trait stability index (MTSI), and a superiority measure. AMMI analysis revealed a significant (p < 0.001) GEI, accounting for 13.82% of the total variation. Genotype performance was variable across the test environments, allowing the selection of best-suited candidates for the target production environment. The environment accounted for a substantial yield variation of 52.62%. The first and second interaction principal component axes accounted for 94.8 and 4.7% of the total variation in the AMMI-2 model, respectively, of surmountable variation due to GEI. The AMMI 2 model family was sufficient to guide the selection of high-yielding and stable genotypes. Based on best linear unbiased predictors (BLUPs), yield stability index (YSI), superiority measure (Pi), and broad adaptation, the following tepary bean genotypes were identified as high-yielding and suited for drought-prone environments: G40138, G40148, G40140, G40135, and G40158. The selected tepary bean genotypes are recommended for cultivation and breeding in Malawi or other related agroecologies.

Effect of Induced Mechanical Leaf Damage on the Yield and Content of Bioactive Molecules in Leaves and Seeds of Tepary Beans (Phaseolus acutifolius).

Growing interest has recently been shown in Tepary beans (Phaseolus acutifolius) because they contain lectins and protease inhibitors that have been shown to have a specific cytotoxic effect on human cancer cells. Bean lectins offer protection against biotic and abiotic stress factors, so it is possible that mechanical foliar damage may increase lectin production. This study evaluates the effect of mechanical stress (foliar damage) on lectin and protease inhibitor content in Tepary beans. Seed yield was also analyzed, and phenolic content and antioxidant capacity (DPPH and TEAC) were determined in the leaves. An experimental design with random blocks of three treatments (T1: control group, T2: 50% mechanical foliar damage and T3: 80% mechanical foliar damage) was carried out. Mechanical foliar damage increased the amount of lectin binding units (LBUs) fivefold (from 1280 to 6542 LBUs in T3) but did not affect units of enzymatic activity (UEA) against trypsin (from 60.8 to 51 UEA in T3). Results show that controlled mechanical foliar damage could be used to induce overexpression of lectins in the seeds of Tepary beans. Mechanical foliar damage reduced seed production (-14.6%: from 1890 g to 1615 g in T3) and did not significantly increase phenolic compound levels in leaves.

Large genomic introgression blocks of Phaseolus parvifolius Freytag bean into the common bean enhance the crossability between tepary and common beans.

The production of the common bean (Phaseolus vulgaris L.), one of the most important sources of protein and minerals and one of the most consumed grain legumes globally, is highly affected by heat and drought constraints. In contrast, the tepary bean (Phaseolus acutifolius A. Gray), a common bean-related species, is adapted to hot and dry climates. Hybridization to introduce complex traits from the tepary bean into the common bean has been challenging, as embryo rescue is required. In this study, we report three novel interspecific lines that were obtained by crossing lines from prior common bean × tepary bean hybridization with Phaseolus parvifolius Freytag in order to increase the male gametic diversity to facilitate interspecific crosses. These interspecific lines enhanced the crossability of the common bean and tepary bean species while avoiding the embryo rescue process. Crossing these three interspecific lines with tepary beans resulted in 12-fold more hybrid plants than crossing traditional common beans with tepary beans. Whole-genome sequencing analysis of these three interspecific lines shows large introgressions of genomic regions corresponding to P. parvifolius on chromosomes that presumably contribute to reproductive barriers between both species. The development of these lines opens up the possibility of increasing the introgression of desirable tepary bean traits into the common bean to address constraints driven by climate change.

Comparative study, homology modelling and molecular docking with cancer associated glycans of two non-fetuin-binding Tepary bean lectins.

We present the purification and characterization of the two most abundant isoforms of lectins isolated from Tepary bean (Phaseolus acutifolius) seeds, which have been shown to differentially affect the survival of different cancer cells. They were separated by concanavalin A-affinity chromatography. After purification, to release the N-glycans, they were digested with the endoglycosidases PNGase and Glycanase A. Fractions resulted from the hydrolysis products were analyzed to determine their carbohydrate composition. Mass spectrometry data indicated that both isoforms contained high mannose glycans being mannose 6 the most abundant form. Furthermore, based on sequence Ans-X-Ser/Thr, where X is any amino acid except proline, a glycosylation site was determined on asparagine 36. When their metal requirement to preserve their biological activity was determined, the lectins showed differences. While lectin A (LA) agglutination activity was best in the presence of magnesium, lectin B (LB) was best with calcium. Additionally, only LA exhibited affinity to human type-A erythrocytes. Although both lectins showed small differences in their properties, an identical structure-model for both lectins was generated by the homology modelling process. Also, the analysis of ligand binding sites and in silico glycosylation were achieved. Molecular docking with colon adenocarcinoma associated-N-glycans revealed some highly possible interactions and, on the other hand, that N-glycan interaction zones of Tepary bean lectins is not restricted to the carbohydrate binding domain but to an extended part of their surface, which could lead new strategies to explain their biological activity.

Comparison of Changing Cultivation Pattern on Morphological and Biochemical Characteristics of Forage of Two Types of Crop Legumes in The Tropical Climate of Southern Kerman Province

Reduction of the quantity and quality of forage is one of the main restrictions on the productivity of livestock systems. Tropical legumes are the most important crops to improve livestock feeds and, thus, for providing livestock products for human consumption in arid regions. In order to investigate the shift of cultivation date of two legumes from summer to spring in arid weather conditions, a factorial experiment in a randomized complete block design with three replication was conducted at the Agricultural Research Institute of south Kerman, Iran, during two cropping seasons. Treatment was planting in three and two tropical legumes (Tapary bean and cowpea). The results showed that changing planting dates led to a significant effect on seed yield and forage quality of two legumes in the region. All agronomic traits for cowpea increased compared to Tepary bean due to differences in their genetic backgrounds. The two legumes were not different in terms of nitrogen, crude protein, and ash. On all three planting dates, the hemicellulose-free cell wall of cowpea was higher than Tepary. In contrast, neutral detergent fiber for Tepary was observed more than cowpea. The highest dry matter index was recorded for cowpea. Whereas the highest dry matter digestibility, the net energy of lactation, and metabolizable energy were related for Tepary. According to the different physiological and phenological responses of the two legumes, it is necessary to examine the selection of suitable planting dates for improving the quantitative and qualitative yield of forage.

Field performance of selected and landrace tepary bean varieties in diverse southwestern USA irrigated production environments

AbstractThe desert Southwest is the oldest area of continuous crop production in the continental USA. Tepary beans (Phaseolus acutifolius A. Gray) were a part of the ancient, irrigated cropping systems, but they were nearly lost during the twentieth century. They are now the subject of heightened research and breeding activity. We wished to ascertain the field performance of varieties improved by selection within the region with those selected outside the region. In one study, the selected varieties were evaluated in two locations across two seasons, and in another, they were evaluated at three locations in the Rio Grande Valley, the principal agricultural production region in New Mexico. A collection of 21 tepary landraces was also examined at the same three locations in the Rio Grande River Valley of New Mexico. Both selected and landrace varieties demonstrated a production capacity above 2000 kg ha−1 under irrigated conditions. Seed size (as determined by 100‐seed weights) was also examined in the selected varieties. Two varieties (TARS Tep32 and CSU148) displayed seed size at the lower range of the small market class of common beans. The developmental phenology of the selected varieties was similar across two seasons. One selected variety, CSU148, also displayed a high level of resistance to powdery mildew during one season favorable for disease development. The other selected varieties exhibited intermediate host‐resistance responses to infection.

Genotypic variation in response to drought stress is associated with biochemical and transcriptional regulation of ureides metabolism in common bean (Phaseolus vulgaris L.)

Ureidic legumes such as common bean (Phaseoulus valgaris L.) plants export nitrogen from the nodules to shoots and leaves as ureides during symbiotic biological nitrogen fixation. Common bean gene encoding allantoinase (allantoin amidohydrolase, EC 3.5.2.5), is a key enzyme that catalyses the hydrolysis of allantoin to allantoic acid. It plays a role in ureide generation for export and ureide catabolism to generate a nitrogen source in sinks tissues. As such, one of the adaptive mechanisms of plants to drought stress, is associated with ureides accumulation. To identify genetic variation of common bean in response to drought stress, changes in the expression of ALLANTONAISE (PvALN) gene and ureides content were examined in the leaf tissues of the three common bean genotypes (CAL96, DAB514 and DAB541) and one tepary bean genotype (Phaseolus acutifolius A.Gray). Amongst all the genotypes, the suggested drought susceptibility in DAB514 common bean genotype, was probably attributed to a repressed PvALN expression rate which were corroborated by an impaired ureides levels, and reduced plant growth. On contrary, drought stress induced an upregulated relative expression of PvALN coupled with an increase in allantoin and allantoate in DAB541 common bean genotype. In addition, the sustained plant growth in CAL96 was probably attributed to a steady amount of allantoin synthesized under drought stress. Taken together, DAB541 and CAL96 common bean genotypes are the promising genotypes with an induced upregulated transcriptional control of catabolism and/or biosynthesis of ureides, hence potential genotypes for selection and introduction under Botswana semi-arid conditions.

Flood tolerance and flood loss predictions for tepary bean across the U.S. Southern Great Plains

AbstractFlooding can cause billions of dollars in crop losses per year. One method to combat susceptibility to flooding is through the identification and use of crops that withstand short flooding events. Tepary bean (Phaseolus acutifolius A. Gray) is an underused crop native to North America and currently grown in small amounts by the indigenous peoples of the Sonoran Desert of northern Mexico and southwestern United States. The genome of tepary bean is being used to improve heat, drought, and pest tolerances in common bean (Phaseolus vulgaris L.) through morpho‐physiological changes to the shoots and roots. This study evaluated the effect of different flooding periods on biomass production and tissue C and N content of tepary bean compared with soybean [Glycine max (L.) Merr.]. The study also defined areas of Kansas and Oklahoma that may flood during periods of 1–3 d and potential effects on the two legumes. The analysis determined that for any 1 yr, 22% of Kansas cropland would flood during a 24‐h period and 16% would flood during a 72‐h (3‐d) period. For Oklahoma, 30% of cropland would flood during a 24‐h period and 25% would flood during a 72‐h period. Although tepary bean withstands the abiotic stresses of high temperature and low precipitation, there was less evidence of flood tolerance. Overall, tepary bean genotypes survive 24‐h flooding events, whereas 72‐h events are detrimental to all traits evaluated. The highly erratic high intensity summer rainfalls common to the Southern Great Plains may reduce the ability of tepary bean to dependably produce biomass. Future breeding efforts should include developing flood tolerance in tepary bean to expand the region of use for this legume.

Interaction of ascorbic acid and 24- epibrassinolide on the level of protein and activity of antioxidant enzymes of catalase and peroxidase on jiropt bean plants (Phaseolus acutifolius) under salinity condition

A group of strong antioxidants, such as ascorbic acid and 24- epibrassinolide have significant environmental effects on plant growth and development. They can cause an increase in plant tolerance to environmental stresses. This research is performed to study the interaction of ascorbic acid and 24- epibrassinolide on the amount of protein and activity of antioxidant catalase enzymes and peroxidase in jiropt bean plants (Phaseolus acutifolius) under salinity. The experiments were performed completely as randomized factorial designs with three concentration of NaCl (0,5,10 %),three concentration of ascorbic acid (0,10,15µm) and Three concentration of 24- epibrassinolide(0,5,10 µm)each one with three replications in greenhouse controlled conditions.The results showed that salinity has a significant and cumulative effect on the protein content and activity of antioxidant enzymes of catalase and peroxidase. The destructive Ascorbic acid-modified effects salt and increases protein content and activity of catalase and peroxidase enzymes, 24-epibrassinolide modified salt effects and caused more increase in protein content and activity of antioxidant enzymes compared to salt treatment, the interaction between ascorbic acid and 24- epibrassinolide on modifying the salt effects were observed in bean plants.

Contrasting Phaseolus Crop Water Use Patterns and Stomatal Dynamics in Response to Terminal Drought.

Terminal drought stress affects more than half of the areas planted with common bean (Phaseolus vulgaris), the main food legume globally, generating severe yield losses. Phenotyping water deficit responses and water use are central strategies to develop improved terminal drought resilience. The exploration and exploitation of genetic diversity in breeding programs are gaining importance, with a particular interest in related species with great adaptation to biotic and abiotic factors. This is the case with tepary beans (Phaseolus acutifolius), a bean that evolved and was domesticated in arid conditions and is considered well adapted to drought and heat stress. Under greenhouse conditions, using one genotype of tepary beans (resistant to drought) and two of common beans (one resistant and one susceptible to terminal drought), we evaluated phenotypic differences in traits such as water use efficiency (WUE), transpiration efficiency, rate of photosynthesis, photosynthetic efficiency, stomatal density, stomatal index, stomatal size, and the threshold for transpiration decline under well-watered and terminal drought conditions. Our results indicate two different water use strategies in drought-resistant genotypes: one observed in common bean aimed at conserving soil water by closing stomata early, inhibiting stomatal development, and limiting growth; and the other observed in tepary bean, where prolonged stomatal opening and higher carbon fixation, combined with no changes in stomata distribution, lead to higher biomass accumulation. Strategies that contribute to drought adaptation combined with other traits, such as greater mobilization of photoassimilates to the formation of reproductive structures, confer bean drought resistance and are useful targets in breeding programs.

Effect of Plant Spacing on Agronomic Performance and Fodder Quality of Four Tepary Bean (Phaseolus acutifolius A. Gray) Cultivars

Tepary bean is gaining interest around the world as a dryland field crop. A two-year field experiment was conducted to determine the effect of plant spacing on the agronomic performance and fodder quality of the crop. A split-plot design was used with three replications, four cultivars (GK010, GK011, GK012, and Motsumi) were assigned to main plots, while subplots were three intrarow plant spacing (10 cm, 20 cm, and 30 cm). Four agronomic variables and eight chemical compositions, including in vitro dry matter digestibility (IVDMD) of husk, stem, and leaf, were measured. Spacing significantly ( P < 0.05 ) influenced plant biomass, pod yield, harvest index, and seed yield, while cultivar affected only pod yield and seed yield. Plant biomass increased with plant spacing where 10 cm produced 936 kg/ha; 20 cm, 750 kg/ha; and 30 cm, 611 kg/ha for 2015–2016 while 10, 20, and 30 cm were observed for 1568 kg/ha, 1135 kg/ha, and 889 kg/ha, respectively, in 2016–2017 season. These trends are attributed to the higher plant population in the narrow row spacing. GK012 consistently outperformed other cultivars for plant biomass, pod yield, and seed yield and has a potential for further selection. Fodder nutritive qualities were not affected by cultivar, while spacing only influenced IVDMD. The three plant parts were significantly ( P < 0.05 ) different for all the nutritive qualities. Leaves had significantly ( P < 0.05 ) lower values of ADF, CF, and NDF compared to those of stem and husk an indication of relatively higher digestibility of the leaf. Acid detergent fiber (40%), neutral detergent fiber (53.65%), crude fiber (35.45%), ash content (12.29%), dry matter (93.09%), and IVDMD (70.66%) were recorded. This study revealed that tepary bean forage has good nutritional content, except for the low phosphorus level. For higher agronomic performance, tepary cultivars should be planted at a spacing of 10 cm without compromising forage quality.

Regulatory Mechanisms of the Resistance to Common Bacterial Blight Revealed by Transcriptomic Analysis in Common Bean (Phaseolus vulgaris L.).

Common bean blight (CBB), primarily caused by Xanthomonas axonopodis pv. phaseoli (Xap), is one of the most destructive diseases of common bean (Phaseolus vulgaris L.). The tepary bean genotype PI 319443 displays high resistance to Xap, and the common bean genotypes HR45 and Bilu display high resistance and susceptibility to Xap, respectively. To identify candidate genes related to Xap resistance, transcriptomic analysis was performed to compare gene expression levels with Xap inoculation at 0, 24, and 48 h post inoculation (hpi) among the three genotypes. A total of 1,146,009,876 high-quality clean reads were obtained. Differentially expressed gene (DEG) analysis showed that 1,688 DEGs responded to pathogen infection in the three genotypes. Weighted gene coexpression network analysis (WGCNA) was also performed to identify three modules highly correlated with Xap resistance, in which 334 DEGs were likely involved in Xap resistance. By combining differential expression analysis and WGCNA, 139 DEGs were identified as core resistance-responsive genes, including 18 genes encoding resistance (R) proteins, 19 genes belonging to transcription factor families, 63 genes encoding proteins with oxidoreductase activity, and 33 plant hormone signal transduction-related genes, which play important roles in the resistance to pathogen infection. The expression patterns of 20 DEGs were determined by quantitative real-time PCR (qRT-PCR) and confirmed the reliability of the RNA-seq results.