Fusarium Verticillioides Strains Research Articles

In vitro production of gibberellic acid and fusaric acid by Fusarium spp. and their role in bakanae disease development

Gibberellic acid (GA3) and fusaric acid (FA) are directly correlated with the symptom development of bakanae disease in rice plants. The role of GA3 and FA, produced in vitro by several Fusarium species associated with bakanae disease, was studied to understand the disease’s etiology and its impact on symptom development. In total, 121 Fusarium strains were obtained from bakanae-infected rice plants collected from various rice cultivation regions in Bangladesh. Finally, 18 highly virulent Fusarium strains were selected based on virulence assay and further evaluated for GA3 and FA production through ultra-performance liquid chromatography analysis. Among the Fusarium strains, Fusarium fujikuroi strains produced a high amount of GA3 and a low amount of FA. In contrast, Fusarium proliferatum and Fusarium verticillioides strains produced a high amount of FA and a low amount of GA3. In exception, the Fusarium strain BD117R of F. fujikuroi produced no GA3 but a high amount of FA. Interestingly, Fusarium commune produced only FA in high concentration. In bakanae disease development, GA3 production was positively related to elongation symptoms whereas FA contributes to stunting symptoms. This is the first record of the production of GA3 and FA by Fusarium species causing bakanae disease of rice in Bangladesh.

Identification of naturally occurring atoxigenic strains of Fusarium verticillioides and their potential as biocontrol agents of mycotoxins and ear rot pathogens of maize

Pre-harvest infection of seed with either of two major ear rot pathogens of maize, Fusarium verticillioides and Aspergillus flavus, leads to high economic losses and detrimental health effects to humans and animals through the production of mycotoxins, fumonisin and aflatoxin, respectively. These carcinogenic compounds are some of the most agriculturally important mycotoxins, consumption of which can lead to various cancers and stunted growth. While atoxigenic strains of A. flavus are used for biocontrol of aflatoxin, no similar biocontrol agent exists for F. verticillioides. We hypothesized that fumonisin non-producing (atoxigenic) F. verticillioides may competitively exclude or antagonize A. flavus and promote plant growth. We screened 150 isolates of Fusarium spp. collected from maize across Texas and identified several F. verticillioides isolates that did not produce fumonisin either in vitro or when grown on maize kernels. Atoxigenic strains of F. verticillioides, 302-A6 and PAL 401, variably affected plant growth following seed coating or soil injection. When pre-applied in a kernel bioassay, both strains significantly inhibited aflatoxin contamination compared to kernels later inoculated only with A. flavus. Applied as a seed coating, neither isolate inhibited aflatoxin or fumonisin accumulation in mature plants. Results confirmed that fumonisin is not required for virulence in Fusarium stalk rot infections. Application of F. verticillioides 302-A6 to developing ears reduced fumonisin accumulation by naturally-occurring toxigenic strains of F. verticillioides. This atoxigenic strain of F. verticillioides and others need to be further investigated to prove their efficacy and potential use as atoxigenic biocontrol agents to reduce fumonisin risk in corn.

Pathogenic and Genetic Characterization of Fusarium verticillioides Strains Collected from Maize and Sorghum Kernels

Commercial and sanitary qualities of cereals are important and contribute to the determination of the final application and destination of the grain and, thus, farmer profit. Although considered a minor crop in Italy, in the last years, the cultivation area of sorghum (Sorghum bicolor L. Moench) has been increasing and is often adjacent or subsequent to the most common maize (Zea mays L.) fields, with the risk of sharing mycotoxigenic fungi that are common to both cereals, such as Fusarium verticillioides. The present work aims to clarify if a fungal physiological characteristic such as fumonisin production and some plant growth parameters such as effects on germination, root and shoot development and on tissue necrosis may be common and shared among F. verticillioides strains belonging to maize and sorghum, especially if present on adjacent fields at the same time. Sorghum kernels are commonly less colonized and contaminated by F. verticillioides and fumonisins than maize, and, at least in part, this aspect could be explained by the higher frequency of low-producing strains obtained from sorghum compared to those obtained from maize. Moreover, although no clear pathogen specificity was found, the results relating to the parameters analyzed suggest a host preference by F. verticillioides isolated from maize that affects maize seedlings with greater severity as well as F. verticillioides strains from sorghum versus sorghum. Five microsatellite markers showed minor differences between the two sets of strains but could not reliably discriminate between hosts. The resulting data suggest that in adjacent maize and sorghum crops, the population of F. verticillioides selected during sorghum cultivation may not represent a particular mycotoxigenic or pathogenic issue for maize cultivation.

Antifungal potential of Azotobacter species and its metabolites against Fusarium verticillioides and biodegradation of fumonisin.

In the study, seven Plant Growth Promoting Rhizobacteria (PGPR) Azotobacter species were screened against three strains of Fusarium verticillioides to test its antifungal activity. Azotobacter strains were tested for the degradation of fumonisin produced by F. verticillioides. Secondary metabolites were isolated and characterized from the Azotobacter strains for the first time. Potential seven Azotobacter species antifungal activity was tested following the dual culture assay against three strains of Fusarium verticillioides namely FVM-42, FVM-86 and MTCC156 estimating the substantial zone of inhibition. Azotobacter species AZT-31 and AZT-50 strains significantly inhibited the growth of F. verticillioides recording drastic growth enhancement of maize under in-vitro conditions by calculating the infection incidence, vigour index and germination percentage. As confirmation, dereplication studies were conducted for the reconfirmation of Azotobacter strains by isolating from rhizoplane. Azotobacter strains played a key role in the degradation of fumonisin produced by F. verticillioides reporting 98% degradation at 2h of incubation with the pathogen. Furthermore, in the study first time, we have tried to isolate and characterize the secondary metabolites from the Azotobacter strains exhibiting six compounds from the species AZT-31 (2) and AZT-50 (4). Preliminary in-vitro experiments were carried out using the compounds extracted to check the reduction of infection incidence (90%) and increase in germination percentage upto 50 to 70% when compared to the test pathogen. Azotobacter strains referred as PGPR on influencing the growth of plant by producing certain substances that act as stimulators on inhibiting the growth of the pathogen. The future perspective would be the production of an active combination of carboxamide compound and Azotobacter species for preventively controlling the phytopathogenic fungi of plants and crops and also towards the treatment of seeds.

Molecular inclusion of Cymbopogon martinii essential oil with β-cyclodextrin as a strategy to stabilize and increase its bioactivity

An essential oil complex (EOP) of Cymbopogon martinii with β-cyclodextrin (β-CD) was evaluated as a strategy to stabilize the essential oil of Palmarosa and increase its bioactivity. The complexation methods used were co-precipitation and kneading, and, for comparison, physical mixing was carried out. To confirm the molecular inclusion, techniques were combined for the characterization of the inclusion complex, such as Fourier Transformer Raman Spectroscopy (FT-Raman), Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA), which suggested the formation of the EOP-β-CD complex with complexation efficiency through the co-precipitation and kneading methods of 77.68% and 47.74%, respectively. Stability of the free and complexed EOP in relation to major compounds (linalool, geraniol, geranyl acetate and caryophyllene) during 14 days of storage was analyzed through Headspace Gas Chromatography coupled with Mass Spectrometry. Geraniol showed stability over the period of evaluation and increased availability when complexed by the Co-precipitation and kneading complex. Furthermore, the antifungal and antitumor activity of the EOP-β-CD complex was evaluated, showing reduced mycelial growth against Aspergillus flavus and Fusarium verticillioides strains compared to the free EOP (percentage of inhibition to toxigenic fungi A. flavus EOP-KM: 29.41%; EOP-CP and EOP-PM: 24.37 and 14.28%, respectively, and, the free EOP with 11.76%). In addition, an interesting activity against tumor cells (HeLa and HT-29) was observed against the tested complexes, which emphasizes the importance of the biotechnological use of β-CD for the stability of natural compounds.

Effect of Carbon Sources on the Production of Volatile Organic Compounds by Fusarium verticillioides.

The aim of the present study was to evaluate the effect of different carbon sources on the hydrocarbon-like volatile organic compounds (VOCs) of Fusarium verticillioides strain 7600 through a Principal Component Analysis approach, and to explore their diesel potential by using data from the literature. The fungus was cultivated in GYAM culture medium, and five carbon sources were evaluated: glucose, sucrose, xylose, lactose, and fructose. The VOCs were collected using a close-loop apparatus and identified through GC-MS. The same profile of 81 VOCs was detected with all treatments, but with different relative percentages among carbon sources. The production of branched-chain alkanes (30 compounds) ranged from 25.80% to 38.64%, straight-chain alkanes (12 compounds) from 22.04% to 24.18%, benzene derivatives (12 compounds) from 7.48% to 35.58%, and the biosynthesis of branched-chain alcohols (11 compounds) was from 6.82% to 16.71%, with lower values for the remaining groups of VOCs. Our results show that F. verticillioides has the metabolic potential to synthesize diesel-like VOCs. Further research should include the optimization of culture conditions other than carbon sources to increase the production of certain groups of VOCs.

Thermogravimetric and Biological Studies of Organotin(IV) Complexes with 4-(Hydroxymethyl)piperidine-1-Carbodithioic Acid

Present studies were conducted to perform thermogravimetric characterization and biological activity investigations of organotin dithiocarbamates of general formulae R3SnL (R = n-Bu, 1; Ph, 2; Cy, 3), R2Sn(Cl)L (R = Me, 4; Ph, 5) and R2SnL2 (R = Me, 6) where L = 4-(hydroxymethyl)piperidine-1-carbodithioate. A novel procedure was also developed for the synthesis of product 2 by direct reflux of 4-(hydroxymethyl)piperidine-1-carbodithioic acid (HL) with triphenyltin(IV) hydroxide. HL was decomposed at low temperatures as compared to the metal complexes. The coordinated products were degraded leaving behind the tin or SnOCl inorganic residues. The products1-6 have shown excellent antimicrobial activities against the tested bacterial (Escherichia coli, Salmonella typhi, Staphylococcus aureus, and Bacillus subtilis) and fungal (Fusarium solani, Aspergillus niger, Alternaria solani, and Fusarium verticillioides) strains. The biological activities were found to depend upon the substitution pattern at the central tin atom.

Antagonistic activity of Trichoderma harzianum and Trichoderma viride strains against some fusarial pathogens causing stalk rot disease of maize, in vitro

ObjectivesA high incidence of stalk rot disease of maize causes huge economic losses as well as deleterious effects on the environment and human health resulting from fungicide use. Against this background, the current study was established to evaluate the antagonistic efficacy of Trichoderma viride and Trichoderma harzianum strains against Fusarium proliferatum and Fusarium verticillioides strains, the most common causative agents of stalk rot disease of maize. MethodsDual culture assay was performed to determine the antagonistic efficacy of Trichoderma strains against some fusarial pathogens of maize. Mycoparasitic relationships of the antagonistic fungal strains against fungal pathogens were investigated using a slide culture technique. Furthermore, a food poisoning technique was performed to detect the antimycotic efficacy of Trichoderma culture filtrates against fusarial pathogens of maize. Antifungal activity of organic solvent extracts of T. harzianum and T. viride was evaluated using the disc diffusion method. GC–MS analysis was used to detect the active components of these extracts. Results and conclusionTrichoderma viride showed antagonistic activity against F. proliferatum and F. verticillioides with mycelial inhibition rates of 80.17% and 70.46%, while T. harzianum exhibited rates of 68.38% and 60.64%, respectively. The culture filtrates of T. viride and T. harzianum strains exhibited antifungal activity against F. verticillioides strain with suppressive rates of 56.7% and 32.2%, while the mycelial inhibition rates against F. proliferatum strain were 44.09% and 23.50%, respectively. Mycoparasitic action of T. harzianum strain against fusarial strains was detected, while no mycoparasitism was observed between T. viride and fungal pathogens. The fungicidal concentration of carbendazim fungicide against F. proliferatum was 2.00 ppm, while F. verticillioides strain exhibited resistance to carbendazim fungicide. Moreover, the acetonic extracts of T. viride and T. harzianum strains exerted the highest antifungal potency against F. proliferatum strain, recording minimum inhibitory concentrations of 0.25 and 0.50 mg/ml, respectively. The main bioactive constituents of the acetonic extracts of T. viride and T. harzianum strains were palmitic acid (22.87%) and acetic acid (21.36%), respectively. In conclusion, the antagonistic strains could be a potential source of novel biological fungicides, especially against carbendazim-resistant F. verticillioides strain, avoiding side effects of chemical fungicides.

Isolation, screening, and molecular identification of lignin-degrading fungi isolates from Cibinong Science Centre, Indonesia Institute of Sciences, Cibinong, West Java

Lignin is a recalcitrant compound that has potential as fuels and chemicals on industries. Contamination of recalcitrant compound with the lignin-like structure on the ecosystem is being concerned worldwide. Fungi is the most targeted organisms with lignin-degrading ability, can secrets laccase and peroxidase to facilitate free radical chain reaction on lignin complex structure. Isolation, screening and identification for isolate with ligninolytic ability is the main purpose of this project. Phylum Ascomycota and Basidiomycota be the main target of this research. Isolation technics that being used are surface sterilization with distilled water and NaClO on PDA medium. Pure culture with ability to grow on lignin minimal medium with black liquor as the only carbon sources then are identified by molecular identification. Isolates that can grow on lignin minimal medium are identified as Fusarium verticillioides strain CBS 127178, Lasiodiplodia sp. LAS-2016 strain CBS 125262, Trichoderma harzianum strain 35814DRJ, and Lasiodiplodia theobromae strain CBS 127106. Four isolates obtained with lignin-degrading ability then preserved by cryopreservation technic for use in the next projects.

A Survey of Mycoviral Infection in Fusarium spp. Isolated from Maize and Sorghum in Argentina Identifies the First Mycovirus from Fusarium verticillioides.

Mycoviruses appear to be widespread in Fusarium species worldwide. The aim of this work was to identify mycoviral infections in Fusarium spp., isolated from maize and sorghum grown in Argentina, and to estimate their potential effects on the pathogenicity and toxigenesis of the host fungus towards maize. Mycoviruses were identified in 2 out of 105 isolates analyzed; Fusarium verticillioides strain Sec505 and Fusarium andiyazi strain 162. They were characterized as members of the genus Mitovirus by high-throughput sequencing and sequence analysis. The F. verticillioides mitovirus was a novel mycovirus whereas the F. andiyazi mitovirus was found to be a new strain of a previously identified mitovirus. We have named these mitoviruses, Fusarium verticillioides mitovirus 1 (FvMV1) and Fusarium andiyazi mitovirus 1 strain 162 (FaMV1-162). To our knowledge, FvMV1 is the first mycovirus reported as naturally infecting F. verticillioides, the major causal agent of ear rot and fumonisin producer in corn. Both mitoviruses exhibited 100% vertical transmission rate to microconidia. The Fa162 strain infected with FaMV1-162 did not show phenotypic alterations. In contract, F. verticillioides Sec505 infected with FvMV1 showed increased virulence as well as microconidia and fumonisin-B1 production, compared with two uninfected strains. These results suggest that FvMV1 could have a role in modulating F. verticillioides pathogenicity and toxin production worth further exploring.

Antifungal activity of Euphorbia species against moulds responsible of cereal ear rots.

This work aimed to identify secondary metabolites from aerial parts of Euphorbia species functional for control of toxigenic Fusarium species responsible of cereal grain rots. Aerial parts of Euphorbia serpens, Euphorbia schickendantzii and Euphorbia collina were sequentially extracted with hexane, ethyl acetate and methanol. The extracts were tested against strains of Fusarium verticillioides and Fusarium graminearum by microdilution tests. The hexane extract of E. collina provided the lowest IC50 s on both fungal species. Further fractionation showed that cycloartenol (CA) and 24-methylenecycloartanol are associated to the moderate inhibitory effect of the hexane extract on fungal growth.Sublethal concentrations of CA and 24MCA blocked deoxynivalenol (DON) and fumonisins production.CA and 24MCA co-applied with potassium sorbate, a food preservative used for Fusarium control, synergized the growth inhibition of fungi. The mixtures reduced mycotoxins accumulation when applied at sublethal concentrations. CA and 24MCA inhibited both fungal growth and mycotoxins production. This fact is an advantage respect to potassium sorbate which increased the mycotoxins accumulation at sublethal concentrations. CA and 24MCA synergized potassium sorbate and their mixtures offer a lower mycotoxigenic risk than potassium sorbate for control of the Fusarium species.

Low Aflatoxin Levels in Aspergillus flavus-Resistant Maize Are Correlated With Increased Corn Earworm Damage and Enhanced Seed Fumonisin.

Preharvest mycotoxin contamination of field-grown crops is influenced not only by the host genotype, but also by inoculum load, insect pressure and their confounding interactions with seasonal weather. In two different field trials, we observed a preference in the natural infestation of corn earworm (CEW; Helicoverpa zea Boddie) to specific maize (Zea mays L.) genotypes and investigated this observation. The field trials involved four maize lines with contrasting levels of resistance to Aspergillus flavus. The resistant lines had 7 to 14-fold greater infested ears than the susceptible lines. Seed aflatoxin B1 (AF) levels, in mock- and A. flavus-inoculated ears were consistent with genotype resistance to A. flavus, in that the resistant lines showed low levels of AF (<30 ppb), whereas the susceptible lines had up to 500 ppb. On the other hand, CEW infestation showed a positive correlation with seed fumonisins (FUM) contamination by native Fusarium verticillioides strains. We inferred that the inverse trend in the correlation of AF and FUM with H. zea infestation may be due to a differential sensitivity of CEW to the two mycotoxins. This hypothesis was tested by toxin-feeding studies. H. zea larvae showed decreasing mass with increasing AF in the diet and incurred >30% lethality at 250 ppb. In contrast, CEW was tolerant to fumonisin with no significant loss in larval mass even at 100 ppm, implicating the low seed aflatoxin content as a predominant factor for the prevalence of CEW infestation and the associated fumonisin contamination in A. flavus resistant maize lines. Further, delayed flowering of the two resistant maize lines might have contributed to the pervasive H. zea damage of these lines by providing young silk for egg-laying. These results highlight the need for integrated strategies targeting mycotoxigenic fungi as well as their insect vectors for enhanced food safety.

Antifungal metabolites from endophytic fungus Fusarium verticillioides strain WF18

Phytochemical analysis of a crude ethyl acetate (EtOAc) extract derived from endophytic fungus Fusarium verticillioides strain WF18 afforded one new polyketide metabolite, fusaisocoumarin A (1), along with two known compounds, emodin (2) and sesquiterpenoid phytohormone (+)-abscisic acid (ABA) (3). Chemical structures of isolated compounds were elucidated based on HRESIMS together with 1D- and 2D-NMR spectroscopic analyses. Interestingly, all isolated compounds revealed pronounced antifungal activity against certain endophytic fungal strains namely; Aspergillus austroafricanus strain Eis.1, Aspergillus versicolor strain EIS2, Phoma fungicola strain AT100, Aspergillus tubingensis strain AN103 along with Candida albicans ATCC 90029 with MIC (minimum inhibitory concentration) range from 0.3 to 1.3 µg/mL. The biosynthesis of antifungal compounds and the phytohormone (+)-abscisic acid (ABA) illustrates an example of the crosstalks between the host plant and its endophyte in which the endophytic fungus produces metabolites defending the host plant against environmental stresses and also against other fungal phytopathogens.

In Vitro Fumonisin Biosynthesis and Genetic Structure of Fusarium verticillioides Strains from Five Mediterranean Countries.

Investigating the in vitro fumonisin biosynthesis and the genetic structure of Fusarium verticillioides populations can provide important insights into the relationships between strains originating from various world regions. In this study, 90 F. verticillioides strains isolated from maize in five Mediterranean countries (Italy, Spain, Tunisia, Egypt and Iran) were analyzed to investigate their ability to in vitro biosynthesize fumonisin B1, fumonisin B2 and fumonisin B3 and to characterize their genetic profile. In general, 80% of the analyzed strains were able to biosynthesize fumonisins (range 0.03–69.84 μg/g). Populations from Italy, Spain, Tunisia and Iran showed a similar percentage of fumonisin producing strains (>90%); conversely, the Egyptian population showed a lower level of producing strains (46%). Significant differences in fumonisin biosynthesis were detected among strains isolated in the same country and among strains isolated from different countries. A portion of the divergent FUM1 gene and of intergenic regions FUM6-FUM7 and FUM7-FUM8 were sequenced to evaluate strain diversity among populations. A high level of genetic uniformity inside the populations analyzed was detected. Apparently, neither geographical origin nor fumonisin production ability were correlated to the genetic diversity of the strain set. However, four strains from Egypt differed from the remaining strains.

The Relationship Analysis on Corn Stalk Rot and Ear Rot According to Fusarium Species and Fumonisin Contamination in Kernels.

Fusarium diseases, including corn root rot, sheath rot, stalk rot, and ear rot are frequently occurring in maize producing areas of China. Fusarium stalk rot and ear rot are the most serious diseases and often occur at the same time, but it is unclear whether there is a correlation between Fusarium composition and disease occurrence. This study was conducted to clarify the relationship between the two diseases. A total of 49 corn stalk rot samples were collected from 15 regions of eight provinces in China from 2016 to 2018. The pathogens were isolated and identified separately from stalks, ear stems, and kernels. The contents of the fumonisins (FB1 and FB2) were detected in kernels. The results showed that the main Fusarium species were found in corn kernels, ear stems and stalks at the same time. The results showed that 1201 strains of Fusarium verticillioides, 668 strains of Fusarium oxysporum, 574 strains of Fusarium graminearum species complex (FGSC), 318 strains of Fusarium equiseti, 95 strains of Fusarium proliferatum, and 40 strains of Fusarium subglutinans were isolated from 1470 corn kernels, 245 ear stems, and 1225 stalks randomly selected from 49 samples. The contamination rate of fumonisins in the 49 samples was 57.1% with an average content of 1.9 μg/g, of which four samples exhibited higher levels as set by the European Commission (4.0 μg/g). These results provide a certain association between stalk rot and ear rot and lay a foundation to study the relationships among Fusarium maize diseases.

Variation in pathogenicity of Fusarium verticillioides and resistance of maize genotypes to Fusarium ear rot

The ineffective control measures of pathogens is due to variability among their populations. Hence, the study of pathogenic variation of Fusarium verticillioides strains on maize genotypes. Six F. verticillioides infected maize ear were randomly obtained from three agro-ecological zones in Southwest Nigeria. Pathogenicity of F. verticillioides strains at 1.0 × 106 spores/mL were examined in vivo based on the rating scale of 1–7 on maize genotypes T2L COMP.1.STR SYN-W-1, PVA SYN 8F2, and T2L COMP.4. The pathogens were inoculated to the maize genotypes on 8th week for disease severity and were all moderately susceptible, however, genotype T2L COMP.4 was the most susceptible. It was observed that, 9.4% were classified as highly virulent, 12.5% as virulent, 37.5% as moderately virulent, 21.8% as slightly virulent, and 18.8% as non-virulent. In all, Fusarium verticillioides strains displayed different degrees of virulence, however, maize genotype T2L COMP.4 was the most susceptible to ear rot.

Role of arbuscular mycorrhizal fungi as biocontrol agents against Fusarium verticillioides causing ear rot of Zea mays L. (Maize)

The protection of plants from pathogens results to better performances in growth and yield characters. Therefore, the efficacy of Glomus clarum and G. deserticola as biocontrol agents against Fusarium verticillioides (AKR 05, ILR 06 and ERW 05) strains on maize T2L COMP.4 was investigated. Concentration 10 g (20 spores), 20 g (48 spores) and 30 g (72 spores) of Glomus clarum and G. deserticola were inoculated separately into 8 kg of soil at four weeks after planting (WAP), with a control (0 g). In addition, spore suspension (1.0 × 106 spores/mL) of Fusarium verticillioides was inoculated at 8 WAP. The treatments were arranged in a completely randomized design with three replicates. The pathogenic effects of F. verticillioides on plant height and shoot weight were significantly reduced by the application of 20 g of G. clarum and 30 g of G. deserticola. Also, 10 g of both G. clarum and G. deserticola significantly enhanced the production of the husk cover, while 30 g G. clarum and G. deserticola significantly reduced the severity of maize ear rot. Therefore, 30 g G. clarum and G. deserticola had biocontrol potential against Fusarium verticillioides. Hence, they are recommended to maize producers in Fusarium endemic agro-ecological zones for optimal production.

Morphological, pathological and mycotoxicological variations among Fusarium verticillioides isolated from cereals.

Among the 194 Fusarium verticillioides isolates screened from 127 cereal samples, 176 were fumonisin producers and others were non-producers. Representative nine Fusarium verticillioides strains along with one reference standard strain MTCC156 were selected to study their morphological, pathological and mycotoxicological variations by conventional and molecular approaches. Fusarium verticillioides strains FVM86, FVM146, FV200 and FVS3 showed significant pathogenicity and also in pigmentation production but varied in fumonisin production. Fusarium verticillioides strain FVP19 recorded variations in all the assays. Fusarium verticillioides strain FVM42 showed drastic phenotypic variation and it also produced fumonisin. Genetic variation among the strains was independent of geographic area of origin but depended on their ability to produce fumonisin. The strains were independent in their cultural characteristics, pigmentation production, pathogenicity assays, fumonisin production and in their genetic variability without having any correlation.

Molecular Variability of &amp;lt;i&amp;gt;Fusarium verticillioides&amp;lt;/i&amp;gt; (Sacc.) in Maize from Three Agro-Ecological Zones of Southwest Nigeria

This study investigated the characterisation of Fusarium verticillioides strains using Amplified Fragments Length Polymorphism (AFLP) EcoR1-G/Mse1-C primer combination. This was done to determine the amount of genetic variability present in F. verticillioides population. The objective of this study is to carry out molecular characterization of F. verticillioides strains from infected ear of maize. Six isolates were obtained in maize ear from 10 locations in three agro-ecological zones of Southwest Nigeria. Polymorphic bands detected were 164 from one base extension of EcoR1 and Mse1 primers in the selective amplification. Primer combination EC + MC produced the highest polymorphic bands of 58, while primer combination ET + MC had the highest percentage polymorphism (100%). Genetic similarity (67%) was observed among strains from Ibadan (IBD) (34, 36), Igbooho (IGH) (39), Ado-Ekiti (EKT) (46, 47), Saki (SAK) (52) and Igboora (IGB) (57, 58, 59 and 60). Strains 19 and 20 from Ilesha (ILH) had the highest pairwise similarity coefficient at 97% grouped in cluster II. The dendrogram delineated F. verticillioides strains into four major cluster groups with 77% similarity and other sub-groups within. Fusarium verticillioides strains could therefore be heterogeneous, and thus amplified fragment length polymorphism is an ideal tool for distinguishing the pathogenic variants of Fusarium verticillioides.

Effect of fumonisin B1 on the emergence, growth and ceramide synthase gene expression of cowpea (Vigna unguiculata (L.) Walp)

Cowpea (Vigna unguiculata) is a nutritious leguminous crop cultivated by many smallholder farmers in developing countries of the world. Fusarium spp. and fumonisin B1 (FB1) are known to be associated with cowpea seed. This study was performed to determine the phytotoxic effects of FB1 on cowpea seedlings and to provide insight on the effect of the toxin on ceramide synthase gene expression. Surface-disinfected seeds were imbibed in FB1 solutions of 5, 20 and 40 mg/L concentrations. Additionally, seeds were artificially inoculated with three different FB1-producing Fusarium verticillioides strains. Percentage emergence was reduced by all three FB1 concentrations and seeds inoculated with F. verticillioides strain MRC 8265. Seedlings imbibed in 40 mg/L FB1 had reduced seedling length whilst seedling mass was reduced by all treatments. Total chlorophyll content was higher in leaves of seedlings raised from seeds imbibed in all three FB1 concentrations when compared to the controls. To evaluate the effect of FB1 on ceramide synthase gene expression, seeds were imbibed in a 20 mg/L FB1 solution. RNA was extracted from untreated and treated samples after 0, 3 and 12 dpi with the latter being divided into shoot and roots samples. Semi-quantitative reverse transcription PCR suggested that there were no significant differences in ceramide synthase gene expression between the control and toxin treated cowpea samples. It thus appears that FB1 did not influence ceramide synthase gene expression in cowpea. Although FB1 exhibited phytotoxic effects on developing cowpea seedlings, the observed physiological and morphological changes were not a result of down regulation of ceramide synthase gene expression.