Serological detection of close and distant relationships of an isolated Tobamovirus

A virus causing mosaic and leaf yellowing symptoms on Mucuna pruriens was isolated and purified through its susceptible host Vigna unguiculata var. TVu 76. Yield of the purified virus obtained was 7.2 mg/kg. It had an ultraviolet (UV) absorption spectrum at 260 nm as 1.53±0.00 and at 280 nm as 1.45±0.00, which translated into nucleic acid content of 72.9 %. Determination of the molecular weight of the virus coat protein from a plotted graph gave 27 kiloDaltons. When the purified virus was electrophoresed in agarose gel, no secondary band was observed. Absorbance curve at 260 nm was obtained when the purified virus was measured spectrophotometrically. A volume of 16 000μL antiserum was obtained against the virus with concentration of 0.3 mg/ml. The titre value determined for the antiserum raised against the virus was 1:2000 as there was a wider difference between the readings obtained for the healthy and diseased controls. At this dilution, the titre value was two and a half times greater than that of the healthy control. The heterologous: homologous percentage (%) obtained for the isolated virus and TMV (Muguga strain) was 50.0 % when Protein-A sandwich enzyme linked immunosorbent assay (PAS ELISA) was used to determine its serological relationship with the virus and other Tobamovirus strains.Keywords: PAS ELISA, Tobamovirus, coat protein, molecular weigh

Biochemical contents of pepper seedlings inoculated with phytophthora infestans and arbuscular mycorrhiza

The effect of interactions between Arbuscular Glomus etunicatum and fungus Phytophthora infestans on biochemical contents of pepper plants was investigated in a greenhouse experiment. The sugar contents (i.e. Glucose fructose and sucrose) were higher in the control and mycorrhizal inoculated pepper seedlings and the lowest in pathogen inoculated seedlings. Free amino acids were the highest in the simultaneously inoculated pepper seedlings while total phenol was found to be the highest in pepper seedlings inoculated with P. infestans. The levels of nitrogen, phosphorus and potassium varied in the inoculated pepper seedlings without any significant difference in the treatment. The results obtained suggest protective influence of mycorrhiza by enhancing the nutritional status of the inoculated pepper seedlings

Reaction of Dioscorea alata (water yam) to anthracnose disease in Nigeria

Anthracnose disease, caused by the pathogen Collectotrichum gloeosporioides Penz., is a serious challenge to the cultivation of Dioscorea alata, a major source of food and income for millions of farm households in the tropics. Five breeder’s lines and eighteen landraces of D. alata from IITA’s germplasm collection were screened in the field in three agroecological zones (southern guinea savanna, derived savannah and the humid forest) of Nigeria for two years. The objective was to study their reactions to anthracnose disease and investigate the influences of environment (E) and genotype x environment (G x E) interactions on these using the Additive Main Effects and Multiplicative Interaction (AMMI) model. Environments (E), obtained as location x year combination, genotypes (G) and G x E interactions were highly significant (P<0.01) for severity of anthracnose disease and accounted for 48, 26.2 and 25.8% of the treatment (G x E combination) sum of squares, respectively. Incidence and severity of foliar symptoms were assessed on three occasions during each growing season. The disease was most severe at Umudike in the humid forest, followed by Ibadan (derived savannah) and Mokwa (southern guinea savannah). The severity was also higher in 1999 across all locations than in 2000. TDa 289 and TDa 294 were identified as the most resistant genotypes. TDa 297, TDa 9500328, TDa 9500197 and TDa 9500010 were stable in their reactions to anthracnose disease across the environments. These lines could be useful in breeding for increased and more stable resistance to anthracnose disease in yam breeding programmes

Distribution of aflatoxigenic Aspergillus section Flavi in commercial poultry feed in Nigeria

The distribution and aflatoxigenicity of Aspergillus section Flavi isolates in 58 commercial poultry feed samplesobtained from 17 states in five agro-ecological zones (AEZs) in Nigeria were determined in order to assess thesafety of the feedswith respect to aflatoxin-producing fungi. Correlation was also performed for incidence of species,aflatoxin-producing ability of isolates in vitro, and aflatoxin (AFB1) concentrations in the feed. A total of1006 Aspergillus section Flavi isolates were obtained from 87.9% of the feed samples and identified as Aspergillusflavus, unnamed taxon SBG, Aspergillus parasiticus and Aspergillus tamarii. A. flavuswas themost prevalent (91.8%)of the isolates obtained from the feed in the AEZs while A. parasiticus had the lowest incidence (0.1%) and wasisolated only froma layer mash sample collected fromthe DS zone. About 29% of the Aspergillus isolates producedaflatoxins in maize grains at concentrations up to 440,500 ?g/kg B and 341,000 ?g/kg G aflatoxins. The incidenceof toxigenic isolates was highest (44.4%) in chick mash and lowest (19.9%) in grower mash. The population ofA. flavus in the feed had positive (r= 0.50) but non significant (p N 0.05) correlations with proportion of toxigenicisolates obtained fromthe feedwhile SBG had significant (p b 0.001) positive (r= 0.99)influence on AFB1 concentrationsin the feed. Poultry feed in Nigerian markets are therefore highly contaminated with aflatoxigenicAspergillus species and consequently, aflatoxins. This is a potential threat to the poultry industry and requires urgentintervention

Influence of Arbuscular mycorrhiza fungi (AMF) on drought tolerance and charcoal rot disease of cowpea

The influence of Arbuscular mycorrhiza fungi (AMF) (Glomus deserticola and Gigaspora gigantea) were evaluated on drought tolerance and charcoal rot disease of cowpea genotypes: IT90K-277-2, IT84S-2246-4 and IT06K123-1. IT90K-277-2 and IT84S-2246-4 were sown in 3 kg of sterilized soil for drought experiment with five treatments. Treatment was established thirty days after germination with inoculation of G. deserticola, the mycorrhizal treated cowpea withstand the water stress and produced high yield. Biocontrol experiment had 2 kg sterilized soil potted into bags with cultivars IT90K-277-2 and IT06K123-1, fourteen treatments were established with soil drenched before planting and simultaneous inoculation. Soil drenched with AMF before planting and inoculation of M. phaseolina after 10 days of germination recorded higher growth parameters, while the simultaneous inoculated plant was the most effective in reducing disease severity. However, simultaneous treatment of G. deserticola, G. gigantea and M. phaseolina were most effective for both growth parameters and reduction of disease severity

Multiple virus infections of lablab [ Lablab purpureus (L.) Sweet] in Nigeria

Leaf samples of Lablab purpureus collected from two agroecological zones of Nigeria—the northern guinea savanna zone (NGSZ) and the derived savanna zone (DSZ)—were infected with viruses when serologically indexed against available antisera. Approximately 31.1 and 81.1% of the leaf samples collected from the NGSZ and DSZ, respectively, were infected. Seven viruses were found: Bean common mosaic virus (BCMV), Cowpea aphid-borne mosaic virus (CABMV), Cucumber mosaic virus (CMV), Cowpea mottle virus (CPMoV), Cowpea severe mosaic virus (CPSMV), Southern bean mosaic virus (SBMV) and Tobacco mosaic virus (TMV) were detected from samples collected from NGSZ, while CMV, CPMoV, Cowpea mosaic virus (CPMV) and CPSMV were detected from samples from DSZ

Persistence of Trichoderma species within maize stem against Fusarium verticillioides

The ability of four Trichoderma isolates to colonize maize stem and persist therein in presence of Fusarium verticillioides were tested in the field. These were three strains of Trichoderma pseudokoningii and one strainof T. harzianum. There were three pairing methods based on the commonly used toothpick inoculation method. This ensures direct introduction of pathogen and antagonist using toothpicks dressed separately with pathogen and antagonists. Maize stems were inoculated with antagonist alone, pathogen alone and sterile toothpicks erved as controls. The proportion of antagonist recovered was plotted against distance moved within maize stem. All Trichoderma isolates had endophytic growth within the maize stem in all pairing methods, giving a significant quadratic response with distance from the inoculation point. Recoveries of antagonists were slightly more in lower than upper internodes. Simultaneous inoculation of pathogen and antagonist gave the best endophytic growth of antagonists. T. harzianum strain 2 and T. pseudokoningii strain 4 had the best endophytic growth in all pairing methods. The pathogen had no effect on endophytic growth of T. pseudokoningii strain 4. T. pseudokoningii strain 4 and T. harzianum strain 2 improved in endophytic growth in the presence of pathogen. Competitive exclusion of F. verticillioides from maize plant using endophytic Trichoderma spp. could be a possibility

Characterisation of a potyvirus from Centrosema pubescens Benth

A virus, 750 × 18 nm, was isolated from Centrosema pubescens from Nigeria, causing leaf malformation, mosaic and mottling on the plant. When inoculated on to various test plants, it failed to produce necrotic or chlorotic lesions on Chenopodium amaranticolor, but symptoms of mottling were observed. The virus did not infect cowpea (Vigna unguiculata varieties IT82E-10, IT84S-2114, Ife brown, TVU 76 or TVU 2657), but produced chlorotic spots, vein clearing and mottling on soybean (Glycine max cultivars Malayan and Samsoy-2). Protein-A sandwich enzyme-linked immunosorbent assay (ELISA) shows that the virus is serologically closely related to Sweet potato feathery mottle virus (SPFMV) genus Potyvirus, Bean yellow mosaic virus (BYMV) genus Potyvirus and Tobacco etch virus (TEV) genus Potyvirus. Comparison of amino acid sequences of the coat protein of the virus with several potyvirus coat protein sequences, using BLAST (Basic Local Alignment Search Tool) analysis, confirmed the relationships. The antiserum raised against the virus had a titre value greater than 1 : 16,000, using antigen-coated plate ELISA. The name Centrosema mosaic virus (CenMoV) for this apparently new Potyvirus is suggested. The consequences of infection of forage legumes with this virus are discussed

Characterisation of a potyvirus from Centrosema pubescens Benth

A virus, 750 /I > 18 nm, was isolated from Centrosema pubescens from Nigeria, causing leaf malformation, mosaic and mottling on the plant. When inoculated on to various test plants, it failed to produce necrotic or chlorotic lesions on Chenopodium amaranticolor, but symptoms of mottling were observed. The virus did not infect cowpea (Vigna unguiculata varieties IT82E-10, IT84S-2114, Ife brown, TVU 76 or TVU 2657), but produced chlorotic spots, vein clearing and mottling on soybean (Glycine max cultivars Malayan and Samsoy-2). Protein-A sandwich enzyme-linked immunosorbent assay (ELISA) shows that the virus is serologically closely related to Sweet potato feathery mottle virus (SPFMV) genus Potyvirus, Bean yellow mosaic virus (BYMV) genus Potyvirus and Tobacco etch virus (TEV) genus Potyvirus. Comparison of amino acid sequences of the coat protein of the virus with several potyvirus coat protein sequences, using BLAST (Basic Local Alignment Search Tool) analysis, confirmed the relationships. The antiserum raised against the virus had a titre value greater than 1 : 16,000, using antigen-coated plate ELISA. The name Centrosema mosaic virus (CenMoV) for this apparently new Potyvirus is suggested. The consequences of infection of forage legumes with this virus are discussed