Cowpea Root Research Articles

Differential responses of certain field pea and cowpea cultivars to root-knot nematode, Meloidogyne incognita for commercial release

BackgroundLegumes are considered staple foods for many countries in different areas of the world. Cultivation of nematode-resistant newly introduced field pea and cowpea cultivars is an important, cheap, and economical way to reduce damaging the nematode population that comes from improper use of nematicides and pesticides.ResultsThe cultivars of two examined crops were planted in pots inoculated with second-stage juveniles of M. incognita under screen house conditions. The results proved significant differences (P ≤ 0.05) among the tested cultivars regarding their responses to M. incognita. Host resistance/susceptibility was rated on the basis of potential reproduction index (PRI). Host reaction was based on average percent reduction potentials of plant growth and yield. The combination between host resistance/susceptibility and host reaction rates was used to give clear and accurate determination to these cultivars. According to the later scale, field pea cultivars were grouped into three categories of highly susceptible (Consessa), moderately susceptible (Diacole), and intolerant cultivars (Cerdon, Samantha and 337), while cowpea cultivars were grouped into two categories of highly susceptible (Kafr El-Sheikh) and susceptible cultivars (Dokki and 331).ConclusionsNone of the tested cowpea and field pea cultivars was found to be resistant or immune to root-knot nematode, M. incognita. Subsequently, plant growth and yield of the tested cultivars seemed to be severely damaged by root-knot nematode that might be attributed to less nutrient uptake by field pea and cowpea roots due to nematode infection. Planting of highly susceptible or susceptible cultivar in progression with resistant cultivars may help in limiting or reducing these defects. This is keeping management processes and production more economical. Further studies are needed to evaluate more cultivars/accessions against root-knot nematode.

Biological Control of Charcoal Rot Disease Caused by Macrophomina phaseolina) Tassi) Goid on Cowpea and Mung Bean by Some Isolates of Streptomyces spp.

Thirty-nine isolates of Actinomycetes were isolated from different sources such as rhizosphere and plant roots of Alfalfa, Clovers, cowpea, Mung bean, sorghum and date palms. Biochemical tests showed that all isolates were gram positive and capable of producing amylase, catalase and gelatinase enzymes. The isolates showed a positive test for gram staining. The isolates were capable of producing the enzymes of amylase, catalase and gelatinase. Dual culture technique showed that Streptomyces griseorubens, S. tendae 6, S. tendae2, S. tendae 5, S. parvulus and S. tendae 6 had high antagonistic activity against Macrophomina phaseolina as a zone of inhibition reached 15, 14, 13, 15, 14 and 12mm, respectively. Molecular identification revealed that actinomycetes isolate No 15, 23, 24 and 30 isolated from rhizosphere of Clovers, Sorghum, Alfalfa, Mung bean had 99% similarity with S. tendae while Actinomycetes No 38 isolated from rhizosphere of Cowpea had 99% similarity with S. grseorubens .and isolate No 27 isolated from date palms had 99% similarity with S.parvulus. all isolate were deposited at NCBI with GenBank accession number LC499602.1, LC499603.1, LC499606.1, LC499607.1, LC499604.1, LC499605.1. The isolate of S. griseorubens showed high efficacy in reducing disease. Which was 10.1% compared with 49.5% in control treatment on cowpea. 22.0% in mung bean compared to 43.4% in control treatment. In the field experiment, the results showed that soil treated with Actinomycetes isolates led to an increase in the percentage of seed germination and reduced the percentage of fungus infection. S. griseorubens reduced the percentage of infection to 11.54% compared to 32.33% in control treatment.

Root Nodule Preparation as a Low-Cost Inoculant for Cowpea

Widely grown in diverse regions of Brazil, cowpea has high nutritional value, is easily cultivated, and can fix nitrogen (N) symbiotically. Although there are commercial inoculants for cowpea, it is difficult for small producers to acquire them. A nodule preparation is an inexpensive and easily prepared option for small farmers. The aim of this study was to test a nodule preparation as a low-cost inoculant, increasing cowpea seed grain production. Thus, different cowpea cultivars were compared in two locations, the municipalities of Crato and Madalena, both in Ceará. Two field experiments were performed to evaluate gain derived from this inoculation method. The nodule preparation was created from nodules removed from roots of cowpea grown in the experimental locations. The nodules were macerated and added to water, obtaining a liquid (inoculant) that was applied to the seeds. The experiment was conducted following a randomized block design with four replicates and a 4 × 3 factorial arrangement (N sources × cultivars). Results indicate little interaction between the sources of N and the cultivars because only the shoot dry matter (Crato experiment) exhibited interaction between both. The differences provided by the nodule preparation were more notable among cultivars and between the environments, Crato and Madalena. The nodule preparation differed little from the commercial inoculant; they were comparable. However, gain in relation to the zero control also proved to be reduced, indicating little contribution of the nodule preparation to cowpea under the conditions tested.

Copper uptake, tissue partitioning and biotransformation evidence by XANES in cowpea (Vigna unguiculata L) grown in soil amended with nano-sized copper particles

The increased application of nanomaterials in agriculture has become an environmental issue due to their toxic impact on plants. The toxicity is linked to the oxidation state of elemental species after plant uptake and recent studies have indicated copper nanoparticles (nCu) to be phytotoxic. So, this study examines the Phytotoxicity of nCu to cowpea (Vigna unguiculata) and its biotransformation using X-ray absorption near edge structure (XANES) technique. Results showed that the agglomerated nCu became phytotoxic to the root and shoot of cowpea at 250–500 mg nCu/kg treatments. Concentration-dependent effects observed for Cu accumulation in roots and shoots were at optimal at 125 mg nCu/kg. XANES analysis of root tissues revealed the biotransformation of Cu from oxidation +1 in nCu after uptake to Cu2+ species in the roots. This mechanism of biotransformation could be either a strategy for mineral storage or detoxification, which will be a subject of further study. Therefore, this study revealed the existence of biotransformation of Cu in the root tissues of cowpea.

Biological control of Rhizoctonia solani in cowpea plants using yeast

Yeasts have been used to manage a large number of plant diseases, but little is known about the mechanisms used by these biocontrol agents. The objectives of the present study were to evaluate the antagonistic effect of yeasts against Rhizoctonia solani and possible mechanisms of action in cowpea plants. Seventy yeast isolates were obtained from leaf, root and stem tissues of cowpea and common bean plants. Screening experiments were conducted in a greenhouse at temperatures ranging from 15 to 26 °C in the first and from 22 to 31 °C in the second experiment. Candida saopaulonensis C6A, Cryptococcus laurentii FVC10 and Bullera sinensis FVF10 (R1) reduced disease severity by 57.4%, 48.5% and 66.3%, respectively. Cowpea plants treated with FVF10 (R1) showed the highest peroxidase and catalase activities. The mechanisms of action were based on competition and induction of enzymes such as peroxidase, catalase and ascorbate peroxidase in cowpea. Candida saopaulonensis C6A, C. laurentii FVC10 and B. sinensis FVF10 (R1) are potential biocontrol agents of damping-off and stem rot caused by R. solani on cowpea plants.

Identifying key contributing root system traits to genetic diversity in field-grown cowpea (Vigna unguiculata L. Walp.) genotypes

Cowpea is a grain legume that is grown extensively as an alternate protein and income source for many smallholder farmers. Characterising cowpea root phenotypes could provide the basis for developing genotypes with root system architecture (RSA) traits that increase soil resource acquisition. Measuring RSA traits of any field crop is a demanding task, in terms of expediency, time, cost, and competence. Targeted root phenotyping strategies focusing on a few relevant traits might aid in side-stepping some of the challenges associated with phenotyping roots of field crops. The objectives of this study were to (i) measure genotypic variation for RSA and shoot traits of cowpea genotypes; and (ii) identify candidate variables and genotypes that contribute the largest share of variance. Sixty cowpea accession were grown in field trials at the University of Cape Coast, Ghana. Seventy variables, mostly quantitative RSA traits were measured. Multivariate analysis was used to determine major traits contributing to variation. There were significant differences (P < 0.05) for the majority of traits evaluated. Fifty-nine traits had coefficients of variation of ≥0.3 among genotypes and were selected for further examination. Broad-sense heritability (H2) estimates were generally intermediate to high and ranged from 0.11 to 0.96. The Shannon-Weaver diversity index (H’) was variable among traits and ranged from 0.00 to 0.88. Shoot and root biomass correlated closely and positively with count- and length- and diameter-related traits. Cluster analysis identified three homogeneous genotype groups and identified groups of cowpea genotypes that could be exploited in breeding programs to improve the genetic basis of root traits. The first nine principal components explained over 74% of total genotypic variation for the twenty-nine traits included in the PCA. Sixteen traits contributed more than other traits to the variability in PC1 and PC2. Soil and root tissue angle-related traits, shoot and root diameter-related traits, root biomass, hypocotyl root length, root count and lateral root density -related traits were among the top 50% of the most important traits contributing to variation and thus warrant consideration in efforts to breed for improved genotypes in cowpea. The workflow presented offers a robust, cost-effective and simple approach to identifying focal root traits that contribute to diversity in grain legumes. The results could potentially facilitate the characterization of specific traits suitable for targeted genotype selection and breeding of new cowpea varieties for efficient RSAs.

Isolation and identification of pathogenic fungi and oomycetes associated with beans and cowpea root diseases in Oman.

The purpose of this study was to characterize fungal and oomycete species associated with root diseases of Phaseolus vulgaris, Vigna unguiculata, V. radiata and Vicia faba in Oman. Root samples were collected from plants suffering from weakened growth and yellowing symptoms. Fungal species were isolated on 2.5% potato dextrose agar amended with 10 mg l−1 rifampicin and 200 mg l−1 of ampicillin and identification was based on sequences of the internal transcribed spacer region of the ribosomal RNA gene (ITS rRNA), glycerol-3-phosphate dehydrogenase (GPDH), translation elongation factor-1 alpha (TEF), beta-tubulin (TUB), calmodulin (CMD), actin (ACT). Isolations yielded 204 fungal isolates belonging to nine different genera, with most isolates belonging to Alternaria and Fusarium. Molecular identification revealed that the isolates belong to 20 fungal species, the most dominant of which was Alternaria alternata. Pathogenicity tests were conducted on each plant species. The inoculations on P. vulgaris revealed that Pythium aphanidermatum induced rotting, damping-off and wilt symptoms while Fusarium equiseti induced yellowing symptoms on the leaves. Rhizoctonia solani produced lesions and root rot on Vigna unguiculata while Curvularia muehlenbeckiae and Curvularia caricae-papayae produced root lesions on the roots of V. unguiculata and V. radiata, respectively. Alternaria alternata produced brown symptoms on the tap root of Vicia faba. P. aphanidermatum resulted in a significant reduction in the fresh weight, dry weight and shoot length of Phaseolus vulgaris. The study shows that several fungal species can be found associated with the roots of beans and Vigna unguiculata in Oman and can result in varying disease symptoms. This is the first report of root lesions produced by Curvularia muehlenbeckiae on the roots of V. unguiculata and by C. caricae-papayae on V. radiata worldwide.

Evaluation of Growth and Morphological Pattern of Mycorrhization in Cowpea [Vigna unguiculata (L.)] Fertilized With Phosphorus

Microorganisms perform important functions in the soil and, among these organisms, the role of arbuscular mycorrhizal fungi (AMF) in plant growth should be highlighted. AMF colonize the roots of most plant species and their beneficial functions in plant development include increased absorption of nutrients from the soil, especially those of low mobility such as phosphorus (P). Evaluating agricultural practices conducted by farmers, such as phosphate fertilization, and observing how they will influence AMF activity in benefiting plant growth should be prioritized. Thus, an experiment was conducted in greenhouse to evaluate the effect of phosphate fertilization on the growth of cowpea plants colonized by AMF and to know which morphological pattern of colonization prevails in their roots. Five P doses and a control treatment, without fertilization, were added to the soil. Cowpea plants respond to phosphate fertilization up to the dose of 240.50 mg P kg-1 soil, for shoot dry mass and in the dose of 150 mg P kg-1 soil, for plant height. The morphological pattern observed in the roots was the intermediate type, characterized by the presence of intra and intercellular hyphae and vesicles, and there was no influence of phosphate fertilization on morphology. High P contents added to the soil led to a reduction in mycorrhizal colonization in cowpea roots.

English

The aim of this research was to evaluate the impact of chromium (III) nitrate on soil microbial activities and growth performance and phytoremediation potentials of two staple leguminous crops, namely cowpea (Vigna unguiculata) and groundnut (Arachis hypogea). Pristine sandy loam soil samples were polluted with nitrate salts of chromium (III) at four different levels (50, 100, 200 and 400 mg/kg) in triplicates. There was a significant (P < 0.05) retarding effect of this metal on the study parameters. A consistent decrease in the total bacterial count in response to increase in dosage of the metal salt was observed. Chromium was also observed to significantly (P<0.05) affect the microbial metabolism as indicated by the decline in microbial respiration shown by the lowering of CO2 evolution in the test samples. There was a reduction in the general growth performance of the two test plants treated with different levels of chromium when compared with the control. Phytoaccumulation experiment showed that only cowpea roots accumulated the pollutant from the 400 mg/kg treated soil, with no metal salt presence in aerial parts of the plants. This chromium-removal potential demonstrated by cowpea makes it a better candidate than groundnut for the phytoremediation of chromium-contaminated soils. Key words: Chromium (III) nitrate, microbial activities, cowpea, groundnut, phytoremediation.

Cowpea (Vigna unguiculata L. Walp) hosts several widespread bradyrhizobial root nodule symbionts across contrasting agro-ecological production areas in Kenya

Cowpea (Vigna unguiculata L. Walp.) is an important African food legume suitable for dry regions. It is the main legume in two contrasting agro-ecological regions of Kenya as an important component of crop rotations because of its relative tolerance to unpredictable drought events. This study was carried out in an effort to establish a collection of bacterial root nodule symbionts and determine their relationship to physicochemical soil parameters as well as any geographical distributional patterns. Bradyrhizobium spp. were found to be widespread in this study and several different types could be identified at each site. Unique but rare symbionts were recovered from the nodules of plants sampled in a drier in-land region, where there were also overall more different bradyrhizobia found. Plants raised in soil from uncultivated sites with a natural vegetation cover tended to also associate with more different bradyrizobia. The occurrence and abundance of different bradyrhizobia correlated with differences in soil texture and pH, but did neither with the agro-ecological origin, nor the origin from cultivated (n = 15) or uncultivated (n = 5) sites. The analytical method, protein profiling of isolated strains by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), provided higher resolution than 16S rRNA gene sequencing and was applied in this study for the first time to isolates recovered directly from field-collected cowpea root nodules. The method thus seems suitable for screening isolate collections on the presence of different groups, which, provided an appropriate reference database, can also be assigned to known species.

English

Roots are essential to plants and can be the focus for yield improvement in the environment the plant grows. The objectives of this study were to evaluate some yield components and root traits in cowpea (Vigna unguiculata (L) Walp) and establish the linear association between the yield and root traits to explore improvement potentials of the crop in humid ecosystem. Ten cowpea accessions were tested in Calabar, Nigeria with humid tropical rainforest ecology. The accessions were grown in perforated polyethylene pipes arranged in completely randomized design, in five replications and on the field arranged in a randomized complete block design, in three replications. TVu-215 had longest roots, heaviest root biomass and largest root volume. TVu-10983, TVu-1515 and TVu-7906 also had long roots. TVu-7857, TVu-1130, TVu-1131, TVu-215 and TVu-1515 had the greatest root density. With respect to yield traits, TVu-1131 and TVu-16196 had the highest yield per hectare; TVu-7857 also had high yield per hectare. Root traits did not significantly correlate with most of the yield traits, but there was significant negative moderate correlation (-0.51) between root volume and number of pods per plant. Root of cowpea does not require much robustness in humid ecology to absorb water and nutrient, which accounts for the non-significant correlation between root system and yield traits in the environment. TVu-16196, TVu-1130, TVu-1131, TVu-215, TVu-7857 and TVu-1515 are selected for the improvement of the root and yield traits. Key words: Cowpea yield traits, root traits, humid tropical ecology, Calabar, Nigeria.

Nodulation and Biomass Yield Response of Cowpea to Row Spacing and Phosphorus Fertilizer Application in the Guinea Savanna Agro-Ecological Zone of Ghana

Phosphorus fertilizer application and planting distance play a major role in the production of shoot, root and nodule dry biomass of cowpea. However, phosphorus is a major limiting nutrient in soils in Ghana. Selection of cowpea varieties that produce good biomass yield under low soil phosphorus or those with high phosphorus response efficiency can be a low input approach in solving this problem in Ghana. Two-season experiments were conducted to evaluate the influence of phosphorus (P) fertilizer and row spacing on growth, nodulation and biomass yield in cowpea. Each of the two experiments comprised of 16 treatment combinations of 4 cowpea varieties, 2 levels of row spacing and 2 levels of P 2 O 5 application laid out in a 4t2t2 factorial experiments in RCBD with four replications. The cowpea varieties were IT t P 148, Valenga, Bengkpla and DPC. The levels of row spacing were 60t20 cm and 40t20 cm, whilst the levels of P were 0 and 30 kg ha -1 P 2 O 5 . The study revealed that varieties DPC and Valenga performed relatively better with respect to shoot and root dry biomass production, number of nodules produced and nodule dry biomass production across both levels of row spacing and phosphorus fertilizer application. The study further established that row spacing of 60t40 cm and P level of 30 kg ha -1 also produced significantly higher quantities of shoot and root dry biomass, number of nodules and nodule dry biomass as compared to row spacing of 40t20 cm and P level of 0 kg ha -1 . For the purpose of producing leguminous fodder crops for feeding livestock, varieties DPC and Valenga should be cultivated for improved animal nutrition. Row spacing of 60t40 cm and phosphorus fertilizer application level of 30 kg ha -1 should also be used for increased biomass yield.

Cowpea Nodules Harbor Non-rhizobial Bacterial Communities that Are Shaped by Soil Type Rather than Plant Genotype.

Many studies have been pointing to a high diversity of bacteria associated to legume root nodules. Even though most of these bacteria do not form nodules with legumes themselves, it was shown that they might enter infection threads when co-inoculated with rhizobial strains. The aim of this work was to describe the diversity of bacterial communities associated with cowpea (Vigna unguiculata L. Walp) root nodules using 16S rRNA gene amplicon sequencing, regarding the factors plant genotype and soil type. As expected, Bradyrhizobium was the most abundant genus of the detected genera. Furthermore, we found a high bacterial diversity associated to cowpea nodules; OTUs related to the genera Enterobacter, Chryseobacterium, Sphingobacterium, and unclassified Enterobacteriacea were the most abundant. The presence of these groups was significantly influenced by the soil type and, to a lesser extent, plant genotype. Interestingly, OTUs assigned to Chryseobacterium were highly abundant, particularly in samples obtained from an Ultisol soil. We confirmed their presence in root nodules and assessed their diversity using a target isolation approach. Though their functional role still needs to be addressed, we postulate that Chryseobacterium strains might help cowpea plant to cope with salt stress in semi-arid regions.

Genome-wide association mapping and agronomic impact of cowpea root architecture.

Genetic analysis of data produced by novel root phenotyping tools was used to establish relationships between cowpea root traits and performance indicators as well between root traits and Striga tolerance. Selection and breeding for better root phenotypes can improve acquisition of soil resources and hence crop production in marginal environments. We hypothesized that biologically relevant variation is measurable in cowpea root architecture. This study implemented manual phenotyping (shovelomics) and automated image phenotyping (DIRT) on a 189-entry diversity panel of cowpea to reveal biologically important variation and genome regions affecting root architecture phenes. Significant variation in root phenes was found and relatively high heritabilities were detected for root traits assessed manually (0.4 for nodulation and 0.8 for number of larger laterals) as well as repeatability traits phenotyped via DIRT (0.5 for a measure of root width and 0.3 for a measure of root tips). Genome-wide association study identified 11 significant quantitative trait loci (QTL) from manually scored root architecture traits and 21 QTL from root architecture traits phenotyped by DIRT image analysis. Subsequent comparisons of results from this root study with other field studies revealed QTL co-localizations between root traits and performance indicators including seed weight per plant, pod number, and Striga (Striga gesnerioides) tolerance. The data suggest selection for root phenotypes could be employed by breeding programs to improve production in multiple constraint environments.

Bradyrhizobium inoculation alters indigenous AMF community assemblages and interacts positively with AMF inoculum to improve cowpea performance

Legumes are a major component in sustainable agricultural systems since they can fix atmospheric nitrogen and form effective associations with both nitrogen fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF). However, the impact of NFB inoculation on the indigenous AMF community structure in legumes has been overlooked. In the current study, we investigated the influence of a Bradhyrhizobium isolate together with a commercial mycorrhizal inoculum on the performance of cowpea, along with its endophytic mycorrhizal community structure. A three-way factorial randomized design was established in sterilized and non-sterilized soils, including control plants (without inoculation), inoculated plants with a Bradyrhizobium (NFB) strain, a commercial mycorrhizal inoculum (AMF) and their combination (AMF+/NFB+). All inoculation treatments under sterile and non-sterile soil conditions resulted in a significant increase in the shoot biomass, which was positively correlated with AMF colonization, and the number of nodules found in cowpea roots. Mycorrhizal colonization and nodule formation in control plants grown in non-sterilized soils, suggested an active and functional local mycorrhizal and rhizobial community in the soil, which was further supported by the molecular fingerprints. Growth of control plants in sterile soil resulted in lower shoot biomass that was in line with the absence of the respective microbial assemblages. Interestingly, the local AMF community pattern of cowpea roots was drastically altered after the NFB application. Molecular fingerprinting, through cloning of PCR amplified sequences of 18sRNA revealed that cowpea plants were colonized by Rhizophagus, Funneliformis, Claroideoglomus and Paraglomus related species. The results support the notion that the introduced Bradyrhizobium strain interacted drastically with the indigenous AMF community, leading to a more diverse colonization pattern of cowpea roots. These findings enhance our understanding of how these microorganisms interact to affect plant performance and increase agricultural sustainability.

Impact Assessment of Neem Compost and Trichoderma harzianum Solution in the Control of Root Knot Nematode Disease on Cowpea

Efficacy of neem leaf based compost andTrichoderma harzianum solution were assessed on root knot nematode pest of two cowpea varieties at the screen house of the International Institute of Tropical Agriculture (IITA), Ibadan during 2012 planting season. The two cowpea varieties which have been confirmed to be susceptible to root knot nematode, IT96D-610 and IT84S-2246-4 were the test crops. The experimental pots (10kg soil) were inoculated with 5,000 root knot nematode eggs. The treatments were neem compost and T. harzianum solution with application rates of 2 ton/ha and 1x10-7 spores respectively. The pots that were not treated served as the control. Each treatment was replicated 4 times while the statistical design was complete randomized design. Data were collected on the growth and yield of cowpea, and also on the nematode populations in the soil and cowpea root. The results indicated that neem compost and T. harzianum solution significantly increased the growth and yield of IT96D-610 and IT84S-2246-4 cowpea varieties grown in the root knot nematode inoculated soil. The populations of root knot nematode in the soil and cowpea root were significantly reduced. The level of root damage (root gall) was significantly reduced in the neem compost and T. harzianum treated cowpea when compared with the untreated control.

Legume shovelomics: High—Throughput phenotyping of common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata subsp, unguiculata) root architecture in the field

Low phosphorus (P) availability and drought are primary constraints to common bean and cowpea production in developing countries. Genetic variation of particular root architectural phenes of common bean is associated with improved acquisition of water and phosphorus. Quantitative evaluation of root architectural phenotypes of mature plants in the field is challenging Nonetheless, in situ phenotyping captures responses to environmental variation and is critical to improving crop performance in the target environment. The objective of this study was to develop flexible high-throughput root architectural phenotyping platforms for bean and cowpea, which have distinct but comparable root architectures. The bean phenotyping platform was specifically designed to scale from the lab to the field. Initial laboratory studies revealed cowpea does not have basal root whorls so the cowpea phenotypic platform was taken directly to field evaluation. Protocol development passed through several stages including comparisons of lab to field quantification systems and comparing manual and image-based phenotyping tools of field grown roots. Comparing lab-grown bean seedlings and field measurements at pod elongation stage resulted in a R2 of 0.66 for basal root whorl number (BRWN) and 0.92 for basal root number (BRN) between lab and field observations. Visual ratings were found to agree well with manual measurements for 12 root parameters of common bean. Heritability for 51 traits ranged from zero to eighty-three, with greatest heritability for BRWN and least for disease and secondary branching traits. Heritability for cowpea traits ranged from 0.01 to 0.80 to with number of large hypocotyl roots (1.5A) being most heritable, nodule score (NS) and tap root diameter at 5cm (TD5) being moderately heritable and tap root diameter 15cm below the soil level (TD15) being least heritable. Two minutes per root crown were required to evaluate 12 root phene descriptors manually and image analysis required 1h to analyze 5000 images for 39 phenes. Manual and image-based platforms can differentiate field-grown genotypes on the basis of these traits. We suggest an integrated protocol combining visual scoring, manual measurements, and image analysis. The integrated phenotyping platform presented here has utility for identifying and selecting useful root architectural phenotypes for bean and cowpea and potentially extends to other annual legume or dicotyledonous crops.

Salt-induced NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; uptake inhibition in cowpea roots is dependent on the ionic composition of the salt and its osmotic effect

Salinity remarkably inhibits NO3 - uptake but the mechanisms are not well understood. This study was addressed to elucidate the role of ionic and osmotic components of salinity on NO3 - influx and efflux employing classic kinetics involving a low affinity transport system (LATS) and a high affinity transport system (HATS). In the presence of KCl, NaCl, and Na2SO4 at 100 mM concentrations, in both LATS and HATS, Michaelis constant (Km) was similar for the three salts and maximum rate (Vmax) decreased as follows: KCl > NaCl > Na2SO4, compared to control indicating a non-competitive interaction with NO3 -. Unexpectedly, iso-osmotic solutions (osmotic potential Ψπ = -0.450) of polyethylene glycol (PEG, 17.84 %, v/v) and mannitol (100 mM) remarkably increased Km in both the LATS and the HATS, but Vmax did not change indicating a competitive inhibition. Under the PEG and mannitol treatments, Km and Vmax were higher than under the salt treatments. The salts increased slightly NO3 - efflux in the following order KCl > NaCl > Na2SO4. In contrast, mannitol strongly stimulated and the PEG inhibited NO3 - efflux. The obtained data reveal that salinity effects were not dependent on the anion type (Cl- versus SO4 2-) indicating a non-competitive inhibition mechanism between Cl- and NO3 -. In contrast, the cation types (K+ versus Na+) had a pronounced effect. The osmotic component is important to net NO3 - uptake affecting remarkably the influx in both LATS and HATS components of cowpea roots.

First Report of Dry Root and Stem Rot of Cowpea Caused by Fusarium proliferatum in the United States

First Report of Dry Root and Stem Rot of Cowpea Caused by <i>Fusarium proliferatum</i> in the United States

Synergistic inhibitory effect of scopoletin and bisdemethoxycurcumin on Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae).

The study aimed to investigate the synergistic activity of scopoletin and bisdemethoxycurcumin (BDMC) against the carmine spider mite Tetranychus cinnabarinus. The acaricidal activities of mixtures of scopoletin and BDMC against T. cinnabarinus female adults were measured via slide dipping and leaf disc dipping. A mathematical model was established by SPSS software. Bioassays for multiple effects including contact, ovicidal, cowpea root intake, repellency and oviposition inhibitory activity were carried out. The optimal mass ratio of the mixture of scopoletin and BDMC (at their respective LC(50)), the median lethal concentration (LC(50)) and the co-toxicity coefficient were 7:6, 0.19 mg/mL and 129, respectively. LC(50) values of contact activities of the mixture at optimal ratio against adults, nymphs, larvae, and eggs were 0.19, 0.18, 0.06, and 1.52 mg/mL, respectively. LC(50) values of cowpea root intake activity against adults and nymphs were 5.62 and 6.52 mg/mL, respectively. The highest repellent rates against adults and nymphs were 69.5% and 72.5%, respectively. The mixture of scopoletin and BDMC at the optimal mass ratio possessed strong acaricidal activity against T. cinnabarinus at various developmental stages.