Seed protein electrophoretic characterization of cowpea (Vigna unguiculata) germplasm from IITA gene bank

Summary The total seed protein, globulin and albumin fractions of 20 cowpea (V. unguiculata) accessions from IITA gene bank were investigated by SDS-polyacrylamide gel electrophoresis. Total seed protein extracts were prepared from the defatted meal by homogenisation and centrifugation in Tris-glycine buffer. The globulins and albumins were obtained from the total protein extract by exhaustive dialysis against sodium acetate buffer. Two main total seed protein electrophoretic patterns were observed with respect to the 39 and 20 kD subunits, which were present in six out of the twenty accessions analysed. While there was no correlation between seed colour and total seed protein banding pattern, the six insect-resistant cultivars were characterized by the presence of the 39 and 20 kD subunits. The globulins were the predominant class of the total seed proteins and consisted mainly of 64, 58, 56 and 14 kD subunits which make up CP1 and CP2, the major globulins. The albumins in all accessions were a heterogeneous protein fraction consisting of both high and low molecular weight subunits. It was suggested that the insect-resistant cultivars may be genetically related and that the 39 and 20 kD subunits may be involved in the insect resistance mechanism.     

Characterization of a cowpea (Vigna unguiculata) rhizobiophage and its effect on cowpea nodulation and growth

A cowpea rhizobiophage (JRW 3 phage) from Jamaican soil was isolated and characterized. The phage has a polyhedral head and a non-contractile tail; maximum adsorption of the phage to the host occurred after 5 min. A one-step growth experiment revealed that the latent period, rise period and burst size of JRW3 phage were 12 h, 16 h, and 28 plaque-forming units/cell, respectively. The JRW 3 phage was highly sensitive to heat, but survived well between pH 5 and 8. The phage was stable in EDTA, though completely inactivated in sodium citrate. Host range analysis showed that 7 of the 40Rhizobium andBradyrhizobium strains tested were sensitive to phage infection. The phage significantly reduced nodule numbers and shoot dry weight of cowpea plants when inoculated with rhizobia in combination with the phage.     

Modelling nitrogen fixation of pea ( Pisum sativum L.)

Abstract

Nitrogen fixation was simulated for a leafless variety (Delta) of pea (Pisum sativum L.) in central Sweden. It is assumed that N₂ fixation is basically proportional to root biomass, but limited by high root N or low substrate carbon concentrations. Input data on root carbon and nitrogen were estimated from observations of above-ground biomass and nitrogen. The simulated N₂ fixation was compared with estimated values from observations using the ¹⁵N labelling technique. Test data were taken from pea monocultures and pea-oat mixtures with varying pea biomass levels during 1999. Simulated within-season accumulated N₂ fixation correlated to the estimated N₂ fixation with a correlation coefficient (R ²) of 0.74. For seasonal simulations, the predictability was higher (R ²=0.93). Two alternative non-dynamic models, estimating seasonal N₂ fixation as proportional to above-ground biomass and above-ground N, respectively, gave lower predictability (R ²=0.83 and 0.80, respectively). The models were also applied to a second year (1998) and two other sites by comparison with accumulated N₂ fixation estimated by the Difference method. A halved specific N₂ fixation rate (expressed per unit of root biomass) in 1999, compared with 1998, corresponded to essentially dryer and warmer soil conditions during 1999. It was indicated that the variations in soil moisture were more important than soil temperature. It was concluded that the abiotic responses might be of great importance for modelling N₂ fixation rate under different soil conditions.     

Deleterious properties of certain rhizosphere bacteria on field pea (Pisum sativum) under gnotobiotic and non-sterile conditions

Three strains of Pseudomonas putida, one non-fluorescent and two fluorescent, were investigated in a series of complementary experiments to characterise their inhibitory effects on peas under different environmental conditions. Firstly, a gnotobiotic growth pouch system was developed to observe the deleterious effects of the strains on pea root development. A negative impact of the strains was observed on the development of the root morphology using these pouches which was accompanied with a subsequent reduction in root biomass. By using this method it was concluded that the deleterious effect of one of the strains was dependent on the inoculum density. Secondly, two complementary studies in non-sterile growth systems where pea seeds/seedlings were inoculated with the bacteria, showed deleterious effects on plant biomass by two of the strains. Thirdly, by using a sterile plant growth system allowing microscopic observations on root hair development, all strains were found to be able to induce root hair deformations on pea seedlings. The results showed that the mode of action for the deleterious effect differ between the strains. Based on our findings, we would like to emphasise the necessity to include a palette of different sterile and non-sterile growth systems to be able to identify characteristics of importance for deleterious rhizosphere bacteria.     

Quick screening of cowpea (Vigna unguiculata) genotypes for aluminium tolerance in an aluminium-treated acid soil

In greenhouse experiments with small pots, seeds of cowpea (Vigna unguiculata) were planted into an acid soil (Oxic Paleudult from Onne, South-East Nigeria) which had been treated with Al₂(SO₄)₃-Cowpea genotypes showed varying seedling growth inhibition within 7 days when grown in soil containing 2.2 meq Al/100 g soil. Soil and plant analysis confirmed, that Al toxicity, and consequently differences in Al tolerance, were responsible for the genotypically different seedling growth responses. 783 genotypes showed a wide range of Al tolerance when screened using this technique. In a long-term pot experiment the effect of Al application to the soil on seed yields of 9 genotypes was studied. Although no significant correlation could be found between depression by Al of seedling growth and grain yield of the genotypes, the same genotypes were classified as most tolerant and most sensitive in both cases. The results show that the simple and quick screening method using Al-treated soil allows the identification of genotypes adapted to soils with high Al supply.     

Agronomic evaluation and identification of potential cowpea (Vigna unguiculata L. Walp) genotypes in South Africa

Cultivar development of cowpea with increased grain yield depends on evaluation and selection of genetically unique and complementary breeding lines. The objective of this study was to evaluate cowpea collections using agronomic traits to select promising parents to develop breeding population. Twenty-two cowpea genotypes were field evaluated using a randomised complete block design with three replications in two locations in South Africa. Analysis of variance revealed significant genotypic (G) and locations (L) differences for all agronomic traits evaluated. Significant differences were also observed for most of the traits due to G X L, G X Year (Y), L X Y and G X L X Y interactions effects. The genotypes tested at two locations showed considerable genetic variation for the following agronomic traits that varied for number of leaves (NL) (20.08–179.78), leaf length (LL) (12.36–67.72 cm), leaf width (LW) (4.78–22.02 cm), number of branches (NB) (6.81–13.85), number of pods per plant (NPPP) (14.33–54.04), number of seeds per pod (NSPP) (11.7286.28), pod diameter (PD) (5.75–22.73 mm), plant height (PH) (6.57–233.71 cm), pod length (PL) (3.94–100.92 mm), hundred seed weight (HSWt) (8.11–49.52 g) and grain yield (GY) (0.10-1.48 t ha^?1). Grain yield was significant and positively correlated with all of the traits except leaf length. The principal component analysis (PCA) identified four principal components (PCs) contributing to 73.62% of the total explained variation amongst the tested genotypes. The selected cowpea genotypes for most of agronomic characteristics are useful and candidate genetic resources for the development of breeding population in cowpea breeding and enhanced production and productivity for food and nutrition in the country.     

Effects of desert dust on yield and yield components of cowpea (Vigna unguiculata L.)

In order to study the effects of desert dust on yield and yield components of cowpea, two field experiments were conducted in the factorial layout based on randomized complete block design with three replicates in Dezful and Mashhad, Iran in 2015. The experimental treatments were combinations of desert dust in three levels (0, 500 and 1500 µg m^?3), numbers of desert dust application (once, twice and thrice) and two types of desert dust. The desert-dust particles were collected during dust storms occurred in Dezful and Zabol, which are the main sources of dust in Iran. The results showed that the biological yield and the grain yield were significantly decreased in both studied sites (Dezful and Mashhad) when the plants exposed to 500 µg m^?3 desert dust treatment compared to normal conditions. Total soluble sugar and proline contents in plant leaf tissues increased significantly when they affected by 1500 µg m^?3 of desert dust, while the plant height was significantly decreased by increasing the desert-dust concentrations at both sites. Biological yield, grain yield, and 100-seed weight were also significantly affected by the desert dust. Overall, the desert dust has adverse effects on yield of cowpea.     

Yield structure components of autumn- and spring-sown pea (Pisum sativum L.)

ABSTRACT

Climate change brings increasing attention to winter sowing of traditionally spring sown crops. Crop stand height, soil coverage, grain yield and yield components of six winter pea varieties and one spring pea variety were compared in eastern Austrian growing conditions in 2014 and 2015. Crop stands of winter pea were taller up to the end of May before they declined and crop stands of spring pea were taller from early June on. Winter pea covered the soil at least partly over winter and showed faster soil coverage in spring. At the end of May, just some weeks before harvest, spring pea attained equal soil coverage. Grain yield of winter pea was almost double that of spring pea due to higher pod density whereas spring pea produced more grains pod^?1 than four out of six winter pea varieties and a higher thousand grain weight than all winter pea varieties. Consequently, grain density was higher for winter pea while the single pod yield was higher for spring pea. Growing winter peas in Central Europe might be a good strategy for increasing grain legume productivity and thereby European feed protein production.     

Mycoflora and fumonisin mycotoxins associated with cowpea [Vigna unguiculata (L.) Walp] seeds

Cowpea seed samples from South Africa and Benin were analyzed for seed mycoflora. Fusariumspecies detected were F. equiseti, F. chlamydosporum, F. graminearum, F. proliferatum, F. sambucinum, F. semitectum, and F. subglutinans. Cowpea seed from South Africa and Benin and F. proliferatum isolates from Benin, inoculated onto maize patty medium, were analyzed for fumonisin production. Samples were extracted with methanol/water and cleaned up on strong anion exchange solid phase extraction cartridges. HPLC with precolumn derivatization using o-phthaldialdehyde was used for the detection and quantification of fumonisins. Cowpea cultivars from South Africa showed the presence of fumonisin B(1) at concentrations ranging between 0.12 and 0.61 microg/g, whereas those from Benin showed no fumonisins. This is believed to be the first report of the natural occurrence of FB(1) on cowpea seed. Fumonisin B(1), B(2), and B(3) were produced by all F. proliferatum isolates. Total fumonisin concentrations were between 0.8 and 25.30 microg/g, and the highest level of FB(1) detected was 16.86 microg/g.     

Plant growth promoting potential of Pontibacter niistensis in cowpea (Vigna unguiculata (L.) Walp.)

During the past couple of decades, understanding of rhizosphere biology has progressed with the discovery of a special group of microorganisms known as plant growth promoting rhizobacteria (PGPR) and its application for sustainable agriculture has increased tremendously in various parts of the world. The search for microorganisms that improve soil fertility and enhance plant nutrition has continued to attract attention due to the increasing cost of fertilizers and some of their negative environmental impacts. In this study we demonstrated, a novel bacterial species Pontibacter niistensis NII-0905 isolated from forest soil in Western ghat forest soil with potential plant growth promoting ability (PGP) such as phosphate solubilization, indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production. The activity varies with different growth temperatures, strain solubilize 28.5 ± 0.9, 48.02 ± 1.9 and 65.07 ± 2.1 μg mL⁻¹ at 4, 15 and 30 °C respectively and produced 24.8 μg mL⁻¹ day⁻¹ of indole acetic acid (IAA) in tryptophan amended media. Qualitative detection of siderophore production and HCN were also detected at all temperature tested. At a lower temperature (4 °C) strain NII-0905 retained all the plant growth promotion attributes. A significant increase in the growth of cow pea was recorded with inoculations of strain NII-0905 in pot experiments. Scanning electron microscopic study revealed the root colonization on cow pea seedlings against the untreated one. These results demonstrate that, the isolate NII-0905 has the promising PGPR attributes for both in cold as well as in humid condition. It has potential as a biofertilizer to enhance soil fertility and promote the plant growth.     

Thermal stability of ascorbic acid and ascorbic acid oxidase in african cowpea leaves ( Vigna unguiculata ) of different maturities

Cowpea, an African leafy vegetable ( Vigna unguiculata ), contains a high level of vitamin C. The leaves harvested at 4-9 weeks are highly prone to vitamin C losses during handling and processing. Therefore, the purpose of this research was to study the effect of thermal treatment on the stability of ascorbic acid oxidase (AAO), total vitamin C content (l-ascorbic acid, l-AA), and dehydroascorbic acid (DHAA) and l-AA/DHAA ratio in cowpea leaves harvested at different maturities (4, 6, and 8 weeks old). The results showed that AAO activity, total vitamin C content, and l-AA/DHAA ratio in cowpea leaves increased with increasing maturity (up to 8 weeks). Eight-week-old leaves were the best source of total vitamin C and showed a high ratio of l-AA/DHAA (4:1). Thermal inactivation of AAO followed first-order reaction kinetics. Heating at temperatures above 90 °C for short times resulted in a complete AAO inactivation, resulting in a protective effect of l-AA toward enzyme-catalyzed oxidation. Total vitamin C in young leaves (harvested at 4 and 6 weeks) was predominantly in the form of DHAA, and therefore temperature treatment at 30-90 °C for 10 min decreased the total vitamin C content, whereas total vitamin C in 8-week-old cowpea leaves was more than 80% in the form of l-AA, so that a high retention of the total vitamin C can be obtained even after heating and/or reheating (30-90 °C for 10 min) before consumption. The results indicated that the stability of total vitamin C in situ was strongly dependent on the plant maturity stage and the processing conditions applied.     

Nitrate alters the flavonoid profile and nodulation in pea (Pisum sativum L.)

A rhizosphere application of NO _inf3 ^sup- and/or naringenin affected the Pisum sativum — Rhizobium leguminosarum biovar viciae symbiosis. NO _inf3 ^sup- (5 mM) lowered while naringenin raised the nodulation status (nodule numbers and weight) and nodule efficiency (C₂H₂ reduction activity). However, the inhibitory effect of NO _inf3 ^sup- was to some extent alleviated when applied in combination with naringenin. The plant biomass was increased by the application of NO _inf3 ^sup- and naringenin, either alone or in combination, while a higher root: shoot ratio was observed only in the naringenin-treated plants. Root flavonoids are known to regulate the expression of nod genes; their high-performance liquid chromatography profile was influenced in different ways by NO _inf3 ^sup- and naringenin.     

Ultra performance liquid chromatography-tandem quadrupole mass spectrometry profiling of anthocyanins and flavonols in cowpea (Vigna unguiculata) of varying genotypes

The structure of flavonoids in food plants affects bioactivity and important nutritional attributes, like micronutrient bioavailability. This study investigated flavonol and anthocyanin compositions of cowpea (Vigna unguiculata) of varying genotypes. Black, red, green, white, light brown, and golden brown cowpea phenotypes were analyzed for anthocyanins and flavonols using ultra performance liquid chromatography-tandem quadrupole mass spectrometry. Eight anthocyanins and 23 flavonols (15 newly identified in cowpea) were characterized. Mono-, di-, and tri(acyl)glycosides of quercetin were predominant in most phenotypes; myricetin and kaempferol glycosides were present only in specific phenotypes. The red phenotypes had the highest flavonol content (880-1060 μg/g), whereas green and white phenotypes had the lowest (270-350 μg/g). Only black (1676-2094 μg/g) and green (875 μg/g) phenotypes had anthocyanins, predominantly delphinidin and cyanidin 3-O-glucosides. Cowpea phenotype influenced the type and amount of flavonoids accumulated in the seed; this may have implications in selecting varieties for nutrition and health applications.     

Silicon effects on nodule growth,dry‐matter production,and mineral nutrition of cowpea (Vigna unguiculata)

Silicon (Si) is not considered as an essential element for plant growth and development but application of Si improved plant growth. In this study, the effect of various concentrations of Si as sodium metasilicate (0, 50, 100, 200, 400, and 800 µg g^–1) on nodule growth and mineral nutrition of Rhizobium sp. U 15–inoculated cowpea (Vigna unguiculata (L.) Walp.) plants grown in pots was studied. Lower additions of Si (50–100 µg g^–1) significantly increased nodule growth (nodule number, nodule fresh weight and dry weight), relative yield of root and shoot, nitrogen, phosphorus, and calcium concentrations. Plant Si concentrations increased with an increase in soil‐applied Si. Nodule growth negatively correlated with higher applied concentrations of Si (200–800 µg g^–1). The results indicate that Si at low concentrations is beneficial for nodule growth.     

Effects of some Nigerian Bradyrhizobium inoculants on the performance of three cowpea cultivars (Vigna unguiculata) in two field plots

Summary We assessed the effectiveness of three locally made lignite, subbituminous coal and cowmanure-based cowpea Bradyrhizobium inoculants in comparison with a peat-based imported Bradyrhizobium incoculant in a two-field plot investigation. The local inoculants were prepared by incorporating three rhizobia strains (Ife CR9, Ife CR15 and Bradyrhizobium japonicum) into each of the above carrier materials and were used to inoculate three cowpea seed varieties: TVU 1190, IT 82E-60 and Ife brown. With lignite-based He CR9 inoculated into TVU 1190 seeds, total N content of the plants was 178.6 mg/plant compared with only 64.3 mg/plant for the uninoculated nitrate-free control plants. With Nigerian lignite, sub-bituminous coal and cow manure as carriers for cowpea rhizobia, the cowpea yield of the inoculated plants increased by 72%, 54% and 10%, respectively, compared with uninoculated plants, while the peat-based inoculant gave a 25% increase in cowpea yield. With lignite-based Ife CR9 inoculated into Ife brown seeds, total N content of the plants was 149.1 mg/plant, but with inoculation by lignite-based B. japonicum, total N content of the treated Ife brown plant was 132.4 mg/plant. Thus, the native Ife CR9 strain seems to be slightly better adapted to tropical conditions than the imported B. japonicum.     

Nutritional evaluation of pea (Pisum sativum L.) protein diets after mild hydrothermal treatment and with and without added phytase

The effect of mild hydrothermal treatment and the addition of phytase under optimal conditions (pH 5.5, 37 degrees C) on the nutritive utilization of the protein of pea (Pisum sativum L.) flour was studied in growing rats by examining the chemical and biological balance. Mild hydrothermal treatment produced reductions of 83, 78, and 72%, respectively, in the levels of alpha-galactosides, phytic acid, and trypsin inhibitors and also produced a significant increase in the digestive utilization of protein. The additional fall in the levels of phytic acid caused by the addition of phytase did not lead to a subsequent improvement in the digestive utilization of protein. The mild hydrothermal treatment of pea flour produced a significant increase in the metabolic utilization of protein and carbohydrates, which was reflected in the protein efficiency ratio and food transformation growth indices. These effects were not observed in the phytase-supplemented pea diet.