Relationship between soil densities ofAspergillusspecies and colonization of wounded peanut seeds

2006 ◽  
Vol 52 (10) ◽  
pp. 951-960 ◽  
Author(s):  
Bruce W Horn
Keyword(s):  
Aspergillus Flavus ◽  
Aspergillus Parasiticus ◽  
Fungal Species ◽  
Aspergillus Species ◽  
Soil Density ◽  
Peanut Seed ◽  
Wound Site ◽  
Seed Colonization ◽  
The Relationship ◽  
Fungal Competition

Soil is a reservoir for Aspergillus flavus and A. parasiticus, fungi that commonly colonize peanut seeds and produce carcinogenic aflatoxins. Densities of these fungi in soil vary greatly among fields and may influence the severity of peanut infection. This study examined the relationship between soil density of Aspergillus species and the incidence of peanut seed colonization under laboratory conditions. Viable peanut seeds were wounded and inoculated with 20 soils differing in composition and density of Aspergillus species and were then incubated for 14 days at 37 °C (seed water activity = 0.92). The effect of soil density of individual section Flavi species (A. flavus strains L and S, A. parasiticus, A. caelatus, and A. tamarii), section Nigri, and A. terreus on the incidence of seed colonization was best expressed as a function of exponential rise to maximum. Exponential curves often rose to maximum percentages of seed colonization by section Flavi species that were well below 100% despite high species densities in some soils. Competition primarily among section Flavi species may explain the reduced incidences of seed colonization. An average of two or fewer propagules of each Aspergillus species in the soil at the wound site was required for colonization of 20% of peanut seeds. Other fungal species were capable of invading peanut seeds only when soil densities of sections Flavi and Nigri species were low.Key words: aflatoxin, Aspergillus flavus, Aspergillus niger, Aspergillus parasiticus, fungal competition.

scholarly journals Production of Bright Greenish Yellow Fluorescence in Figs Infected by Aspergillus Species in California Orchards

Plant Disease ◽  
1998 ◽  
Vol 82 (6) ◽  
pp. 669-673 ◽  
Author(s):  
Mark A. Doster ◽  
Themis J. Michailides
Keyword(s):  
Aspergillus Flavus ◽  
Uv Light ◽  
Fungal Species ◽  
Fungal Strain ◽  
Aspergillus Species ◽  
Yellow Fluorescence ◽  
Greenish Yellow ◽  
Relationship Of ◽  
The Relationship ◽  
Aspergillus Section

The relationship of bright greenish yellow fluorescence (BGYF) of dried figs under longwave UV light to colonization by Aspergillus fungi was determined. BGYF in naturally infected figs was associated with decay by only four fungal species: the aflatoxin-producing species Aspergillus flavus (both L and S strains) and A. parasiticus, and the aflatoxin nonproducers A. tamarii and A. alliaceus. BGYF was more likely to be visible internally (after cutting open the fig) than externally. For all four species associated with BGYF, some infected figs did not show BGYF. The absence of fluorescence is probably not associated with the fungal strain or isolate involved, since isolating Aspergillus spp. from nonfluorescent figs followed by inoculating other figs with these isolates resulted in BGYF. Many of the nonfluorescent figs had small fungal colonies (<7 mm in diameter), even though some figs with large colonies were also nonfluorescent. The additional colonization of figs by other fungi did not affect the occurrence of BGYF in figs colonized by fungi in Aspergillus section Flavi. Figs infected with A. flavus or A. parasiticus and showing no BGYF were occasionally contaminated with aflatoxin, while other figs showing BGYF and infected with A. flavus or A. tamarii had no aflatoxins. Although not as promising as originally hoped, BGYF might be of use to remove aflatoxin-contaminated figs for certain specific situations in California.

scholarly journals Occurrence of Aflatoxigenic Aspergillus Species in Various Varieties of Peanuts Produced in Western Kenya

2017 ◽  
Author(s):  
Menza C. Nelson ◽  
Muturi W. Margaret ◽  
Lucy Kamau
Keyword(s):  
Aspergillus Flavus ◽  
Dominant Species ◽  
Aspergillus Parasiticus ◽  
Cyclopiazonic Acid ◽  
Aspergillus Species ◽  
Western Kenya ◽  
Central District ◽  
Aspergillus Section

Aflatoxin contaminates foods including peanuts. Aflatoxin is a carcinogenic toxin mainly produced bty Aspergillus flavus. Other Aspergillus species that rarely produce aflatoxins are A. nomius and A. niger. Aflatoxin is associated with liver failure, hepatocellular carcinoma (HCC) and death. Recent studies have shown that peanuts in Kenya are highly contaminated with aflatoxins but information gaps exist on the characterization of the Aspergillus species that produce aflatoxins in peanuts in Kenya. Therefore, this gap necessitated the determination of the Aspergillus species producing aflatoxins in peanuts from the main growing districts of Busia and Kisii Central districts. One hundred and two (102) peanuts samples were collected from farmers&rsquo; in each district Aspergillus species were isolated from the peanut samples by using the dilution plate technique on modified Rose Bengal agar. Phenotypical characterization of the identified Aspergillus section flavus isolates from the peanuts samples was determined using the procedure of Mellon and Cotty. This study identified five (5) Aspergillus species as contaminants in peanuts analyzed in this study. They were Aspergillus flavus L-strain, Aspergillus flavus S-strain, Aspergillus parasiticus, Aspergillus niger and Aspergillus tamari. Overall, the occurrence of Aspergillus flavus L- strain and A. flavus S- strain were significantly higher than other species identified (H = 15.55, df = 4, P = 0.004) in peanuts from the two districts. However, A. flavus S-strain was the most dominant species identified in the study with a mean occurrence of 45.1%. Aspergillus flavus L- strain was the most common isolate (58.8%) in peanuts from Busia district while A. flavus S- strain was the most common strain (60.2%) in peanuts from Kisii Central district. Overall, the occurrence of Aspergillus flavus L strain and A. flavus S strain were significantly higher than other species identified (H = 15.55, df = 4, P = 0.004) in peanuts from the two districts. However, A. flavus S-strain was the most dominant species (F=3.15, df =25, P=0.031) with an overall mean occurrence of 45.1%. The confirmation of occurrence of other species that produce toxins such as A. niger and A. tamarii which also produces cyclopiazonic acid suggests the need to screen peanuts for other carcinogenic mycotoxins.

Aqueous Extracts of Tulbaghia violacea Inhibit Germination of Aspergillus flavus and Aspergillus parasiticus Conidia

2011 ◽  
Vol 74 (6) ◽  
pp. 1007-1011 ◽  
Author(s):  
BENESH MUNILAL SOMAI ◽  
VUYOKAZI BELEWA
Keyword(s):  
Aspergillus Flavus ◽  
Plant Extract ◽  
Cell Walls ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Aspergillus Parasiticus ◽  
Fungal Species ◽  
Dependent Manner ◽  
Transmission Electron ◽  
Cellular Components

Aspergillus flavus and Aspergillus parasiticus are important plant pathogens and causal agents of pre- and postharvest rots of corn, peanuts, and tree nuts. These fungal pathogens cause significant crop losses and produce aflatoxins, which contaminate many food products and contribute to liver cancer worldwide. Aqueous preparations of Tulbaghia violacea (wild garlic) were antifungal and at 10 mg/ml resulted in sustained growth inhibition of greater than 50% for both A. flavus and A. parasiticus. Light microscopy revealed that the plant extract inhibited conidial germination in a dose-dependent manner. When exposed to T. violacea extract concentrations of 10 mg/ml and above, A. parasiticus conidia began germinating earlier and germination was completed before that of A. flavus, indicating that A. parasiticus conidia were more resistant to the antifungal effects of T. violacea than were A. flavus conidia. At a subinhibitory extract dose of 15 mg/ml, hyphae of both fungal species exhibited increased granulation and vesicle formation, possibly due to increased reactivity between hyphal cellular components and T. violacea extract. These hyphal changes were not seen when hyphae were formed in the absence of the extract. Transmission electron microscopy revealed thickening of conidial cell walls in both fungal species when grown in the presence of the plant extract. Cell walls of A. flavus also became considerably thicker than those of A. parasiticus, indicating differential response to the extract. Aqueous preparations of T. violacea can be used as antifungal treatments for the control of A. flavus and A. parasiticus. Because the extract exhibited a more pronounced effect on A. flavus than on A. parasiticus, higher doses may be needed for control of A. parasiticus infections.

scholarly journals Aflatoxin Production by Aspergillus flavus and A. parasiticus on Visibly Sound Rehydrated Peanut, Corn and Soybean Seed1

1984 ◽  
Vol 11 (1) ◽  
pp. 43-45 ◽  
Author(s):  
David M. Wilson ◽  
Durham K. Bell
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Soybean Seed ◽  
Aflatoxin Production ◽  
Limiting Factors ◽  
Peanut Seed ◽  
Corn Seed ◽  
The Mean

Abstract Peanut, corn and soybean seed were inoculated with 14 isolates of Aspergillus flavus Link and A. parasiticus Speare. The seeds were hand sorted to remove all visibly damaged seeds and were fumigated under vacuum (-95.25 k Pa Hg) with 2.2% cyano (methylmercuri) guanidine at 37 C for 48–96 hours. All fumigated seed had a minimum of 95% germination and a maximum of 5% residual contamination by fungi and bacteria. Corn and peanut samples (100 g/flask) were rehydrated to 28% moisture and inoculated with all isolates; soybean samples (100 g/flask) were rehydrated to 28% moisture and inoculated with four A. flavus and two A. parasiticus isolates. Samples were incubated for 10 days at 30 C and analyzed for aflatoxins. Aspergillus parasiticus isolates produced aflatoxin B1, B2, G1 and G2 while A. flavus isolates produced aflatoxin B1 and B2. Mean B1 production for 12 isolates was 34 mg/kg in peanut seed and 3.6 mg/kg in corn seed. Two A. flavus isolates produced 3.8 to 5.4 mg/kg B1 in peanut seed, and 2.2 mg/kg in corn seed. Overall, the mean B1 production was about 10 times higher on peanut seed than on corn seed. However, more G1 was produced on soybean seed than B1. The isolate and the substrate are apparent limiting factors in aflatoxin production. Peanut seed accumulated more aflatoxin than corn or soybean seed when inoculated with the same isolates and incubated under similar conditions.

scholarly journals Investigation of the Antifungal and Anti-Aflatoxigenic Potential of Plant-Based Essential Oils against Aspergillus flavus in Peanuts

2020 ◽  
Vol 6 (4) ◽  
pp. 383
Author(s):  
Premila Narayana Achar ◽  
Pham Quyen ◽  
Emmanuel C. Adukwu ◽  
Abhishek Sharma ◽  
Huggins Zephaniah Msimanga ◽  
...  
Keyword(s):  
Essential Oils ◽  
Aspergillus Flavus ◽  
High Performance ◽  
Opportunistic Infections ◽  
Aflatoxin Production ◽  
The United States ◽  
Microscopy Study ◽  
Aspergillus Species ◽  
Gas Chromatography Mass Spectrometry ◽  
Ammonia Vapor

Aspergillus species are known to cause damage to food crops and are associated with opportunistic infections in humans. In the United States, significant losses have been reported in peanut production due to contamination caused by the Aspergillus species. This study evaluated the antifungal effect and anti-aflatoxin activity of selected plant-based essential oils (EOs) against Aspergillus flavus in contaminated peanuts, Tifguard, runner type variety. All fifteen essential oils, tested by the poisoned food technique, inhibited the growth of A. flavus at concentrations ranging between 125 and 4000 ppm. The most effective oils with total clearance of the A. flavus on agar were clove (500 ppm), thyme (1000 ppm), lemongrass, and cinnamon (2000 ppm) EOs. The gas chromatography-mass spectrometry (GC-MS) analysis of clove EO revealed eugenol (83.25%) as a major bioactive constituent. An electron microscopy study revealed that clove EO at 500 ppm caused noticeable morphological and ultrastructural alterations of the somatic and reproductive structures. Using both the ammonia vapor (AV) and coconut milk agar (CMA) methods, we not only detected the presence of an aflatoxigenic form of A. flavus in our contaminated peanuts, but we also observed that aflatoxin production was inhibited by clove EO at concentrations between 500 and 2000 ppm. In addition, we established a correlation between the concentration of clove EO and AFB1 production by reverse-phase high-performance liquid chromatography (HPLC). We demonstrate in our study that clove oil could be a promising natural fungicide for an effective bio-control, non-toxic bio-preservative, and an eco-friendly alternative to synthetic additives against A. flavus in Georgia peanuts.

scholarly journals Aflatoxin contamination in food crops: causes, detection, and management: a review

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Abhishek Kumar ◽  
Hardik Pathak ◽  
Seema Bhadauria ◽  
Jebi Sudan
Keyword(s):  
High Temperature ◽  
Aspergillus Parasiticus ◽  
Fungal Species ◽  
Aflatoxin Contamination ◽  
Food Crops ◽  
Farming Practices ◽  
Resistant Varieties ◽  
Food Commodities ◽  
Post Harvesting ◽  
Favorable Conditions

AbstractMycotoxins are secondary metabolites produced by several fungal species and molds. Under favorable conditions like high temperature and moisture, they contaminate a large number of food commodities and regional crops during pre and post-harvesting. Aflatoxin is the main mycotoxin that harm animal and human health due to its carcinogenic nature. Aflatoxins are mainly released by Aspergillus flavus and Aspergillus parasiticus. AFB1 constitutes the most harmful type of aflatoxins and is a potent hepato-carcinogenic, mutagenic, teratogenic and it suppresses the immune system. To maintain food safety and to prevent aflatoxin contamination in food crops, combined approaches of using resistant varieties along with recommended farming practices should be followed. This review concentrates on various aspects of mycotoxin contamination in crops and recent methods to prevent or minimize the contamination.

scholarly journals Seed Tolerance in Peanuts (Arachis hypogaea L.) to Members of the Aspergillus flavus Group of Fungi1

1978 ◽  
Vol 5 (1) ◽  
pp. 53-56 ◽  
Author(s):  
J. A. Bartz ◽  
A. J. Norden ◽  
J. C. LaPrade ◽  
T. J. DeMuynk
Keyword(s):  
Arachis Hypogaea ◽  
Aspergillus Flavus ◽  
Peanut Seed ◽  
Test Fungus ◽  
Arachis Hypogaea L ◽  
Aspergillus Flavus Group ◽  
Apparent Susceptibility

Abstract An assay of cured, hand-shelled seeds of various peanut genotypes for tolerance to members of the Aspergillus flavus group of fungi has been performed in Florida for the years 1971–1974. The assay involved exposing peanut seed at 20–30% moisture to conidia of A. parasiticus or A. flavus in petri plates and incubating at 25 C. After 1 week, the percentage of the seeds with sporulating colonies of the test fungus was determined. Typically, individual lines or cultivars were evaluated on the basis of the average of three plates. However, second or third assays of the same seed lots were done on 45 occasions during the 4 year period. More than 95% of these repeated assays yielded data similar to those from the original assay. However, different seed lots of the same line also were assayed and did not always yield similar results unless the dates of digging, methods of curing and location of the plantings were the same. Some shifts in susceptibility were quite extreme. One lot of stackpole cured ‘Altika’ resulted in 12% colonized seeds in the assay but 77% of a windrow-cured seed lot, dug on the same day from the same plot had colonies of the test fungi. No particular change in the harvesting procedure was consistently associated with increases or decreases in apparent susceptibility. Based on tests of all seed lots of 15 commonly grown cultivars during the years 1971–1974. ‘Florunner’ was the most tolerant cultivar and ‘Tifspan’ was the most susceptible.

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