Cowpea Root Research Articles

Assessment of dynamic microbial community structure and rhizosphere interactions during bioaugmented phytoremediation of petroleum contaminated soil by a newly designed rhizobox system

To understand the plant (Vigna unguiculata) and plant-growth promoting bacteria (PGPB) (Microcococcus luteus WN01) interactions in crude oil contaminated soil, experiments were conducted based on the newly designed rhizobox system. The rhizobox was divided into three main compartments namely the rhizosphere zone, the mid-zone, and the bulk soil zone, in accordance with the distance from the plant. Plants were grown in these three-chambered pots for 30 days under natural conditions. The plant root exudates were determined by analyzing for carbohydrates, amino acids, and phenolic compounds. The degradation of alkane, polycyclic aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPHs) were quantified by GC-FID. Soil catalase, dehydrogenase, and invertase activities were determined. The microbial community structure was assessed using denaturing gradient gel electrophoresis (DGGE). Results showed that the inoculation of M. luteus WN01 significantly enhanced cowpea root biomass and exudates, especially the phenolic compounds. Bioaugmented phytoremediation by cowpea and M. luteus promoted rhizodegradation of TPH. Cowpea stimulated microbial growth, soil dehydrogenase, and invertase activities and enhanced bacterial community diversity in oil contaminated soil. The rhizosphere zone of cowpea inoculated with M. luteus showed the highest removal efficiency, microbial activities, microbial population, and bacterial community diversity indicating the strong synergic interactions between M. luteus and cowpea.

Root litter decomposition in a sub-Sahelian agroforestry parkland dominated by Faidherbia albida

In agroforestry systems, fine roots grow at several depths due to the mixture of trees and annual crops. The decomposition of fine roots contributes to soil organic carbon stocks and may impact soil fertility, particularly in poor soils, such as those encountered in sub-Sahelian regions. The aim of our study was to measure the decomposition rate of root litter from annual and perennial species according to soil depth and location under and far from trees in a sub-Sahelian agroforestry parkland.Soil characteristics under and far from the trees were analysed from topsoil to 200 cm depth. Faidherbia tree, pearl millet and cowpea root litter samples were buried in litterbags for 15 months at 20, 40, 90 and 180 cm depths.Root litter decomposition was mainly impacted by soil moisture and soil depth. Faidherbia decomposed more slowly (36 ± 12% remaining mass after 15 months) than cowpea and pearl millet roots (23 ± 7% and 29 ± 11% respectively). Pearl millet aboveground biomass, at harvesting time, was twice as high under (992 g m−2) than far (433 g m−2) from the tree, and belowground biomass (0–200 cm of depth) was 30.9 g m−2 and 19.6 g m−2 under and far from the tree, respectively. Faidherbia fine roots contributed slightly (p-value < 0.1) to higher stocks of C under the tree (7761 ± 346 g m−2) than far from it (5425 ± 558 g m−2) and from 0 cm down to 200 cm depth.

Host suitability of summer cover crops to Meloidogyne arenaria, M. enterolobii, M. incognita and M. javanica

Summary Cover crops can be a useful tool for managing plant-parasitic nematodes provided they are poor or non-hosts for the target nematode species. A glasshouse experiment was done to determine the host status of four common cover crops in Florida, sunn hemp, cowpea, sorghum sudangrass and sunflower, to pure populations of four common tropical root-knot nematode (RKN) species Meloidogyne javanica (Mj), M. incognita (Mi), M. enterolobii (Me) and M. arenaria (Ma). Tomato was included as a susceptible control. Eight weeks after nematode inoculation (WAI), tomato showed the highest root gall damage for all tested RKN species, with gall indices (GI) between 7 (Ma) and 8.5 (Me) and reproduction factor (RF) ranging from 20 (Ma) to 50 (Mj). No visible root galls were observed for any of the RKN species on sunn hemp and sorghum sudangrass at 8 WAI. However, Mj and Mi were able to reproduce slightly on sorghum sudangrass (RF = 0.02 and 0.79, respectively). Sunflower and cowpea were infected by all four tested RKN species, but host suitability varied. Sunflower root galling ranged from 1.1 (Me) to 4.5 (Mj) and RF = 3.2 (Me) to 28.7 (Mj), while cowpea root galling ranged from 0.6 (Mi) to 5.1 (Me) and RF = 0.8 (Mi) to 67.3 (Mj). Sunn hemp and, to a lesser extent, sorghum sudangrass were poor hosts to all four tested RKN species. Sunflower was a good host to all RKN species, but root gall damage and RF were lowest for Me. Cowpea was a good host to Mj, Me and Ma, but a poor host to Mi. Our results confirm and stress the importance of RKN species identification when selecting cover crops as an RKN management strategy.

Influence of Groundnut and Rice Activated Charcoals Addition on Oil Polluted Soil and Mobility of Heavy Metals in the Root and Shoot of Vigna unguiculata L. Walp in the Tropical Rainforest

In Nigeria, spent oil destroys crops, contaminate farmland, aquaculture and drinking water. It also alters the soil properties, leads to deficit of water and oxygen, shortages of soil nutrients like N and P, adsorbs to soil particles and reduces porosity and aeration of soil. The study aims to determine the potential of groundnut hull (GAC) and rice husk (RAC) activated charcoal in biodegradation of spent lubrication oil in soil with reduction in mobility and bioaccumulation of heavy metals in the tissues of the cultivated cowpea (Vigna unguiculata L. Walp) plants. Experimental units were set up in a screen house containing cowpea seedlings planted in different soil treatments: polluted, unpolluted as well as RAC and GAC remediated polluted soil, each in 5 replicates. Mobility and bioaccumulation of the heavy metals in the root, shoot and seeds of the cowpea were analyzed. Cd, Cr and Pb were below detectable limit (BDL), Cu was 0.21 and Zn was 0.26 mg/kg in unpolluted soil while the levels of heavy metals were elevated in spent oil polluted soil: Cd 0.1, Cr 0.25, Pb 0.12, Cu 0.7 and Zn 0.63 mg/kg. RAC treatments significantly decreased the mobility and bioaccumulation of the heavy metals in the root (F3, 14 = 19.338, Sig = 0.00 (p &lt; 0.05) so also, GAC significantly decreased the heavy metals mobilization and bioaccumulated in the cowpea roots (F3, 14 = 91.224, Sig = 0.000 (p &lt; 0.05). RAC and GAC are potential effective and low cost phytoremediation materials.

The effects of a combined amendment on growth, cadmium adsorption by five fruit vegetables, and soil fertility in contaminated greenhouse under rotation system

Cadmium (Cd) exposure is related to a multitude of adverse health outcomes because food crops grown on Cd-polluted soil are widely consumed by the public. The present study investigates the different application techniques of a combined amendment (lime + zeolite + biochar + compost, LZBC) for soil Cd immobilization effect on growth performance, Cd uptake by the second season crops, and soil quality in greenhouse vegetable production (GVP) under a rotation system. Five fruit vegetables were cultivated as the second season crop in the same plots which have been used for pakchoi as the first season crop (with or without LZBC application). The results indicated that LZBC with the consecutive application (T3) promoted crops biomass and fruit yield the most, followed by LZBC with the second crop application (T2) and LZBC with the first crop application (T1). LZBC application showed increasing rhizosphere soil pH and improvement in soil fertility of all crops including available nitrogen, available phosphorus, available potassium, organic matter, and cation exchange capacity. LZBC had positive influences on soluble sugar, soluble protein, and vitamin C in edible parts of 5 vegetables. Cd contents in fruit, shoot, and root of eggplant, pimento, cowpea, and tomato except cucumber were reduced by adding LZBC. As for the economic performance, T3 had the highest output/input ratio in general. Overall, these results demonstrated that T3 was dramatically more effective for minimizing health risk, increasing production, and facilitating sustainable utilization of soil under the Cd-contaminated GVP system.

Multi-Wall Carbon Nanotubes, Metal Oxide and Hydroxy-Apatite Nanoparticles Enhanced Plant Growth Promoting Capabilities of Root Endosymbionts of Cowpea (Vigna unguiculata (L.) Walp.).

The present study was aimed to evaluate the effect of three different nanomaterials (NMs) on the growth, physiology and protein profile of the endosymbiotic bacteria isolated from the root nodules of vegetable cowpea. The alterations in growth and viability of the bacterial cells, their indole-acetic acid (IAA) and siderophore production abilities, phosphate solubilization potential and total protein content were assessed. Further, the isolates were also analyzed for changes in their exopolysaccharide (EPS) production and secretion behavior with exposure to different concentrations of the NMs. The NM supplementation of the broth improved the growth, viable cell count, IAA content, siderophore production and potential to solubilize tri-calcium phosphate (TCP) as sole phosphorus (P)-source. The NMs also improved the total protein content of the bacterial cells indicating the improved physiology and biochemistry of the treated bacterial cells. The treated cells produced significantly high EPS compared to untreated control cultures. The present investigation revealed that the NMs improved plant growth abilities of cowpea root endosymbiotic bacteria, though the impact varied across various isolates as well as NM concentrations.

Responses of oil degrader enzyme activities, metabolism and degradation kinetics to bean root exudates during rhizoremediation of crude oil contaminated soil

During rhizoremediation process, plant roots secrete the specific exudates which enhance or stimulate growth and activity of microbial community in the rhizosphere resulting in effective degradation of pollutants. The present study characterized cowpea (CP) and mung bean (MB) root exudates and examined their influences on the degradation of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) by the two oil degraders Micrococcus luteus WN01 and Bacillus cereus W2301. The effects of root exudates on soil microbial population dynamic and their enzymes dehydrogenase (DHA), and catechol 2,3 dioxygenase (C23O) activities were assessed. Both root exudates enhanced the degradation by both oil degraders. Cowpea root exudates maximized the removal of TPHs and PAHs by M. luteus WN01. Both bacterial population and DHA increased significantly in the presence of both root exudates. However, the C23O activities were significantly higher in WN01 treated. No significant influence of root exudates was observed on the C23O activities of W2301 treated. By using gas chromatography -mass spectroscopy, the dominant compounds found in cowpea and mung bean root exudates were 4-methoxy-cinnamic acid and terephthalic acid. Found in lower amount were propionic, malonic acid, and citric acid which were associated with enhanced PAHs desorption from soil and subsequent degradation. Novelty statement This is the first study to characterize the low molecular weight organic acids from root exudates of cowpea and mung bean and their influences on hydrocarbon desorption and hence enhancing the biodegradation process. The findings of the present study will greatly contribute to a better understanding of plant-microbe interaction in total petroleum hydrocarbons contaminated soil.

Co-inoculations with rhizobia and arbuscular mycorrhizal fungi alters mycorrhizal composition and lead to synergistic growth effects in cowpea that are fungal combination-dependent

Cowpea can effectively form tripartite symbiotic associations with nitrogen-fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) although the selection of compatible AMF species and rhizobial strains which are promoting cowpea growth remains a challenge. The aims of the current study were 1) to evaluate the response of cowpea plants to a symbiotic NFB and a multi-AMF inoculum and 2) to explore any interaction between the symbiotic NFB and the different AMF isolates. In a pot gnotobiotic trial, cowpea plants grown under limited N supply, were inoculated with or without a symbiotic nitrogen-fixing bacterium, Sinorhizobium meliloti, and combinations of three different AMF species namely Dominikia disticha, Claroideoglomus etunicatum and Rhizophagus irregularis. Experimental evaluation was determined through the measurement of above ground biomass, nutrient content and AMF root colonization. The presence of AMF species on cowpea roots was also determined with cloning and sequencing. Inoculation with both AMF and S. meliloti led to increased cowpea biomass production compared to inoculation with AMF only, but the presence of a positive effect depended on the specific AMF partners used. Inoculation with AMF alone had a highly positive impact on the growth and P uptake of cowpea, but the NFB inoculation was needed to address N deficiency in planta. The presence of both symbionts generally led to increased AMF colonization of the cowpea roots, however, plant colonization depended on the AMF species, and became even negative, when all three AMF inocula were used together. The AMF composition in plant roots was also altered in the presence of the S. meliloti. Plant nitrogen content of cowpea plants significantly increased under the presence of both symbionts compared to AMF alone, while phosphorus content was hardly affected by dual inoculations. The results show positive synergistic effects of the different AMF species and S.meliloti. Inoculation with all AMF isolates and S. meliloti led to high above ground biomass production and accumulation of N. The presence of S. meliloti increased P content in plants not inoculated with AMF. Finally, the efficiency of synergism depends on the specific AMF partners used and it is not related to their colonization levels.

Influence of Mycorrhizal Inocula on Cowpea Root Colonization and Soil Improvement in Kano, Nigeria

Influence of Mycorrhizal Inocula on Cowpea Root Colonization and Soil Improvement in Kano, Nigeria

Combined Application of Inoculant, Phosphorus and Potassium Enhances Cowpea Yield in Savanna Soils

Low soil phosphorus levels in savanna soils of Ghana limit cowpea response to inoculation. A two-year experiment was carried out on 2 soil types of the Guinea and Sudan savanna zones of Ghana based on the hypothesis that Bradyrhizobia inoculant (BR3267) in combination with phosphorus and potassium fertilizer will significantly increase cowpea root nodulation, growth and yield. The study aimed to determine the effect of phosphorus and potassium fertilizer on cowpea response to Bradyrhizobia inoculant. The treatments were laid out in Randomized Complete Block Design, replicated four times. The plot size was 8 × 3 m, with the sowing distance of 60 × 20 cm. The treatment comprises of commercial Bradyrhizobia inoculant, phosphorus (0, 30, 40 kg P2O5 ha−1) and potassium (0, 10, 20, 30 K2O ha−1). Application of Bradyrhizobia inoculant with 30 kg P2O5 ha−1 and 20 kg K2O ha−1 gave the highest grain yield (1.68 and 1.86 tons ha−1) at both soils which did not differ from the yield obtained from BR-40-30 kg ha−1 P2O5 and K2O ha−1 on the Ferric Lixisol and BR-40-20 kg ha−1 P2O5 and K2O on the Ferric Luvisol. The same treatment also gave the highest nodule number and nodule dry weight. The results of this study have shown that the application of Bradyrhizobia inoculant followed by P and K fertilizer was effective for cowpea growth in field conditions.

In vitro Inorganic Phosphate Solubilization Tests of Cowpea Root Nodule Bacteria from Ethiopia

Background: Phosphorus is one of the limiting plant nutrients in most soil due to its fixation with metal ions both in acidic and alkaline soil. However, some soil bacteria have potential to solubilize the cation-fixed phosphorus and make it available to plants.Methods: Sixty-six cowpea root nodule bacterial species were tested for inorganic phosphate solubilization (PS). PS potential of the isolates from Ca3 (PO4)2, AlPO4 and FePO4 were tested on four different kinds of agar media. Solublization efficiency was determined as Solubilization Index (SI) on agar media and quantity of bioavailable phosphorous on broth media. Result: About 30% of the bacterial isolates, out of which 60% endophytes were Ca3 (PO4)2 solubilizers on Pikovskaya medium but did not grow on media containing AlPO4 and FePO4 as sole P sources. Isolates showed significant variation (p less than 0.05) in Ca3 (PO4)2 solubilization efficiency on the different culture media and ECE-21 (Pseudomonas putida) was versatile in solubilizing Ca3(PO4)2 from the four test media. However, ECE-26A (Bacillus subtilis) showed the highest PS in broth media (140.8 µg ml-1) indicating the moderate correlation (r=0.5578; p less than 0.05) of PS between solid and liquid media. Amounts of P solubilized and pH change of the culture filtrate was inversely correlated (r=-0.731; p less than 0.01). In general, ECE-21 was the most efficient P solubilizer (SI=2.67±0.1; P=87.74±7.4µg ml-1) solublizers and hence can be an ideal candidate as inoculants for the crop production in Ethiopia after field evaluation.

Application of biochar and inorganic phosphorus fertilizer influenced rhizosphere soil characteristics, nodule formation and phytoconstituents of cowpea grown on tropical soil

The effect of biochar alone or co-applied with triple superphosphate on rhizosphere soil characteristics, nodule formation, phytoconstituents and antioxidant property of cowpea (Vigna uguiculata) is yet to be adequately examined in sub Saharan Africa. A field experiment was conducted where cowpea (Vigna unguiculata) was grown in a tropical sandy loam soil amended with biochar at 1.5 t ha−1 and 2.5 t ha−1 solely or together with inorganic phosphate fertilizer (Triple superphosphate), applied at a rate of 60 kg P ha −1. At 50% flowering, changes in selected rhizosphere soil properties (pH, total nitrogen, available phosphorus, soil organic carbon, cation exchange capacity), nodule count, phytochemicals (phenols, flavonoids, alkaloids, tannins, saponins) and antioxidant property of cowpea roots and leaves were determined by standard laboratory procedures. Differences between means of the measured parameters were established using ANOVA, and relationships among the parameters were explored using Pearson correlation (p < 0.05). Addition of biochar solely or in combination with TSP significantly (p < 0.05) increased soil pH, total nitrogen, available phosphorus, soil organic carbon, cation exchange capacity and root nodule count. Flavonoids, phenols, alkaloids, saponin, tannin contents and antioxidant activity in the roots and leaves were significantly (p < 0.05) higher in the amended soils compared with the unamended soil. Similarly, soil flavonoids, phenols, alkaloids and antioxidant activity were significantly higher in amended soils compared with control. Significant, positive inter and intra correlation with varying strength was found between soil properties, nodule number and phytoconstituents. This is an indication that biochar can be co-applied with triple superphosphate to sustain soil fertility, improve nodulation and enhance concentrations of phytoconstituents in soil, cowpea roots and leaves.

Study of Root and Stem Rot Pathogen (Rhizoctonia solani) in Different Culture Media, Host Range and Effect of Weather Parameters on Disease Incidence

Root and stem rot of cowpea caused by Rhizoctonia solani is one of the most important problems for farmers among the coastal regions of Odisha. Keeping this in view, the behavioural study of the pathogen was done by studying its growth pattern in different culture media and host medium. Among five different media, Potato dextrose agar (90.00 mm) was found to support the maximum radial growth followed by Sabouraud’s dextrose agar medium (87.90 mm), Potato dextrose rose Bengal agar (82.40 mm), Oat meal agar (76.60 mm) and Malt extract agar (70.98 mm). In study of meteorological parameters in relation to disease development the maximum incidence was recorded in October at a maximum temperature of 32.7°C, minimum temperature 22.9 °C accompanied by night RH 92% and day RH 64%. However, weather parameters under study did not yield any significant effect on disease development. However, the soil factors like sandy loam textured soil and acidic to neutral PH contributed towards this soil borne disease. Among host range studies, Rhizoctonia solani isolated from cowpea could infect rice (Oryza sativa), maize (Zea mays), tomato (Solanum lycopersicum), chilli (Capsicum annum), brinjal (Solanum melongena), field pea (Pisum sativum), cucumber (Cucumissataivus), bengalgram (Cicer arietinum), arhar (Cajanus cajan), cotton (Gossypium hirsutum), and groundnut (Arachis hypogea) in addition to its own host.

Potential of biocontrol agents against Ganoderma lucidum causing basal stem rot in mesquite (Prosopis cineraria) in arid regions of India

This study investigates the potential of native biocontrol agents (BCAs) as controls against Ganoderma lucidum causing root rot mortality in Indian mesquite. The disease is prevalent in sandy soils where trees grow under rainfed conditions. In addition, a beetle namely Acanthophorus serraticornis damages the roots, resulting in increasing vulnerability of the host thereby allowing easy of the pathogen. In dual culture tests, Ganoderma infected cowpea root bit experiment and compatibility with insecticides revealed that the three BCAs (Trichoderma longibrachiatum, T. harzianum, and Aspergillus nidulans) significantly inhibited G. lucidum mycelial growth. The highest mycelial growth inhibition (47.6%) was recorded after 96 h followed by 39.8% and 29.3% at 72 and 48 h, respectively, by T. longibrachium. Cell free filtrates of T. longibrachiatum, T. harzianum, and A. nidulans were superior in inhibiting mycelium growth. A low concentration (3 ml) of T. longibrachiatum was more effective in inhibiting mycelium growth compared to other BCAs. Both Prosopis juliflora compost and onion residue compost amendments as food substrates favored the growth of these BCAs, which ultimately reduced the viability of Ganoderma-colonized root bits of cowpea. Studies on compatibility between insecticides and BCAs suggests that T. longibrachiatum, harzianum and A. nidulans can be combined with phorate or chloropyriphos (both organophosphates) at variable concentrations if amended together for partially infected trees, or as a prophylactic measure in healthy trees. These studies demonstrate that there is considerable opportunity for using native BCAs against G. lucidum in managing root rot disease.

Impact of palm oil mill effluent (POME) on the populations of rhizobium and meloidogyne species in Awka, Nigeria

The impact of palm oil mill effluent (POME) on the populations of Rhizobium and Meloidogyne species was tested at the Teaching and Research Farm of Nnamdi Azikiwe University Awka, Nigeria. Three cowpea cultivars ,Dan Kano, Borno local and Sokoto local were used as target crops on plots that received 0 l/ha(control),4000l/ha,6000l/ha and 8000l/ha levels of POME applications. The treatments combinations were randomized within each block and replicated three times. Generally, increasing level of POME application increased number of functional root nodules in all the cultivars, but decreased length of roots and number of non- functional nodules. Nematode populations drastically decreased with increase in POME quantities. Both Rhizobium and Meloidogyne species compete for establishment sites on cowpea roots and high POME rates decreased Nematode population which is why all the three cowpea cultivars had their highest yields at 8000l/ha POME application rate. So POME, an organic waste from oil palm processing can be used at up to 8000l/ha to effectively control obnoxious root knot nematode and enrich soil for crop cultivation especially Sokoto local cowpea cultivar.&#x0D; Keywords: POME (palm oil mill effluent), Rhizobium, Meloidogyne liters/hectare, cowpea cultivars

PATHOGENICITY OF Macrophomina SPECIES COLLECTED FROM WEEDS IN COWPEA

ABSTRACT Charcoal rot caused by Macrophomina phaseolina is a major cowpea disease causing substantial losses to growers. In the semi-arid region of Brazil, cowpea is one of the most widely used alternatives for crop rotation during the off-season of melon. This favors Macrophomina multiplication because both crops are hosts of this pathogen. The objective of this study was to verify the pathogenicity of Macrophomina phaseolina and M. pseudophaseolina on cowpea. The Macrophomina spp. isolates used were obtained from the roots of Trianthema portulacastrum and Boerhavia diffusa, weed species prevalent in melon production areas in North-east Brazilian. The experiment was carried out in a greenhouse. Cowpea plants cv. ‘Paulistinha’ were inoculated with 30 M. phaseolina isolates, 30 M. pseudophaseolina isolates and a reference isolate of M. phaseolina obtained from cowpea roots. All Macrophomina isolates were able to cause disease on cowpea and there were no statistical differences between both Macrophomina species regarding disease incidence and severity. Moreover, 65.2 and 100.0% of the M. phaseolina isolates, and 56.2 and 92.8% of the M. pseudophaseolina isolates, obtained from T. portulacastrum and B. diffusa, respectively, were as severe to cowpea as the M. phaseolina reference isolate from cowpea. These results emphasize the need to establish management practices aiming to control T. portucalastrum and B. diffusa from cowpea production areas, as they can act as potential sources of inoculum and survival for Macrophomina spp.

GRAIN YIELD AND MICROBIOLOGICAL QUALITY OF COWPEA PLANTS GROWN UNDER RESIDUAL EFFECT OF SEWAGE SLUDGE FERTILIZATION1

ABSTRACT Cowpea plants produce protein-rich grains and present high yield potential when grown under irrigation and organic fertilization, enabling to substitute part of the mineral fertilizer with sewage sludge, reducing costs and generating environmental benefits. Thus, a field study about residual effect of sewage sludge fertilization on cowpea was developed to evaluate this substitution. The experiment was conducted using a randomized block design with four replications, in a 2×5 factorial arrangement consisted of two fertilization types (residual effect of sewage sludge fertilization, and mineral fertilizers) and five cowpea cultivars (BRS-Pajeu, BRS-Xiquexique, BRS-Marataoa, BRS-Pujante, and BRS-Cauame). The residual fertilizations were from applications of sewage sludge and NPK mineral fertilizers for pineapple crops grown in the area before the cowpea crop. The experiment was conducted using 80,000 plants ha-1 and micro-sprinkler irrigation. Vegetative and yield components, grain yield, and microbiological quality were analyzed. BRS-Pujante had the highest cowpea grain yield (4,124 kg ha-1) and the highest means for vegetative and yield components. The soil with residual sewage sludge fertilization improved the cowpea root growth and grain yield (3,854 kg ha-1); the latter was 19% higher than that of treatments with mineral fertilization. These results were related to the great soil organic matter content provided by the sludge fertilization, which promotes nutrient mineralization, increasing grain yield. Fresh and dry grains of cowpea plants grown under residual effect of sewage sludge fertilization have similar microbiological quality to those of plants grown under mineral fertilization.

Isolation and Identification of ACC Deaminase Producing Bacteria from Rhizosfer and Plant Roots of Maize, Cowpea, and Groundnut Growing under Saline Stress

ACC deaminase producing bacteria reduces the excess ethylene produced by stressed plant because ACC deaminase catalyzes the cleavage of ACC into ammonium and α-ketobutyrate. ACC deaminase is produced by several rhizospheric and endophytic bacteria. This study was aimed to obtain ACC deaminase producing bacteria isolated from rhizosfer and plant roots of maize, cowpea, and groundnut growing under saline stress. Isolation was conducted by surface plating on NA medium. Qualitative selection was based on the growth of isolate on DF salts medium supplemented with AIB. Quantitative selection based on ACC deaminase activity assay. Identification of the isolates was carried out by morphologycally and sequencing of 16S rRNA gene. Isolation and selection resulted four bacterial isolates (AJG3, RJG6, ATL5, and RTN10). Those bacterial isolates have the ACC deaminase activity between 184.65 to 692.54 nmol α-ketobutyrate. mg−1. h−1. Isolate of AJG3, RJG6, and ATL5 were gram negative bacteria, only one isolate was gram positive bacteria (RTN10). Based on 16S rRNA gene sequence, AJG3, RJG6, ATL5, and RTN10 isolates have a high similarity with Klebsiella variicola, Rhizobium pusense, Agrobacterium tumefaciens, and Bacillus stratosphericus respectively.

EFFECT OF NEEM COMPARED WITH PSEUDOMONAS FLUORESCENS ON THE MANAGEMENT OF COWPEA ROOT ROT DISEASE

Cowpea also known as 'black eye beans' (Vigna ungiculata L.) is an important leguminous and hay crop in tropical and subtropical regions. In recent years root rot caused by Macrophomina phaseolina causes significant losses in cowpea. Hence, the present study was undertaken to assess the bio-potential of neem cake with Pseudomonas fluorescens on the management of cowpea root rot disease. In this study, P. fluorescens as seed and soil application (@ 10 gm/kg and 2.5 kg/ha) with neem oil cake as soil application @ 0.25 t/ha (T6) significantly reduced the root rot disease incidence with a maximum per cent disease reduction and increased the biometrics of cowpea plant under both pot and field trials. Keywords: Macrophomina phaseolina, cowpea, neem, in-vivo.

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.