scholarly journals Variation in Competitive Ability Among Isolates of Aspergillus flavus from Different Vegetative Compatibility Groups During Maize Infection

2010 ◽  
Vol 100 (2) ◽  
pp. 150-159 ◽  
Author(s):  
H. L. Mehl ◽  
P. J. Cotty
Keyword(s):  
Aspergillus Flavus ◽  
Competitive Ability ◽  
Aflatoxin Contamination ◽  
Vegetative Compatibility ◽  
Life Strategy ◽  
Nucleotide Polymorphisms ◽  
Vegetative Compatibility Groups ◽  
Kernel Infection ◽  
Aflatoxin B ◽  
Maize Kernels

Aspergillus flavus, the primary causal agent of aflatoxin contamination, includes many genetically diverse vegetative compatibility groups (VCGs). Competitive ability during infection of living maize kernels was quantified for isolates from 38 VCGs. Kernels were inoculated with both a common VCG, CG136, and another VCG; after 7 days (31°C), conidia were washed from kernels, and aflatoxins and DNA were extracted from kernels and conidia separately. CG136-specific single-nucleotide polymorphisms were quantified by pyrosequencing; VCGs co-inoculated with CG136 produced 46 to 85 and 51 to 84% of A. flavus DNA from kernels and conidia, respectively. Co-inoculation with atoxigenic isolates reduced aflatoxin up to 90% and, in some cases, more than predicted by competitive exclusion alone. Conidia contained up to 42 ppm aflatoxin B1, indicating airborne conidia as potentially important sources of environmental exposure. Aflatoxin-producing potential and sporulation were negatively correlated. For some VCGs, sporulation during co-infection was greater than that predicted by kernel infection, suggesting that some VCGs increase dispersal while sacrificing competitive ability during host tissue colonization. The results indicate both life strategy and adaptive differences among A. flavus isolates and provide a basis for selection of biocontrol strains with improved competitive ability, sporulation, and aflatoxin reduction on target hosts.

scholarly journals Influence of the Host Contact Sequence on the Outcome of Competition amongAspergillus flavusIsolates during Host Tissue Invasion

2011 ◽  
Vol 77 (5) ◽  
pp. 1691-1697 ◽  
Author(s):  
H. L. Mehl ◽  
P. J. Cotty
Keyword(s):  
Competitive Ability ◽  
Competitive Exclusion ◽  
Aflatoxin Contamination ◽  
Host Tissue ◽  
Nucleotide Polymorphisms ◽  
Tissue Invasion ◽  
Genetic Types ◽  
Attachment Sites ◽  
Host Infection ◽  
Maize Kernels

ABSTRACTBiological control of aflatoxin contamination byAspergillus flavusis achieved through competitive exclusion of aflatoxin producers by atoxigenic strains. Factors dictating the extent to which competitive displacement occurs during host infection are unknown. The role of initial host contact in competition between pairs ofA. flavusisolates coinfecting maize kernels was examined. Isolate success during tissue invasion and reproduction was assessed by quantification of isolate-specific single nucleotide polymorphisms using pyrosequencing. Isolates were inoculated either simultaneously or 1 h apart. Increased success during competition was conferred to the first isolate to contact the host independent of that isolate's innate competitive ability. The first-isolate advantage decreased with the conidial concentration, suggesting capture of limited resources on kernel surfaces contributes to competitive exclusion. Attempts to modify access to putative attachment sites by either coating kernels with dead conidia or washing kernels with solvents did not influence the success of the first isolate, suggesting competition for limited attachment sites on kernel surfaces does not mediate first-isolate advantage. The current study is the first to demonstrate an immediate competitive advantage conferred toA. flavusisolates upon host contact and prior to either germ tube emergence or host colonization. This suggests the timing of host contact is as important to competition during disease cycles as innate competitive ability. Early dispersal to susceptible crop components may allow maintenance withinA. flavuspopulations of genetic types with low competitive ability during host tissue invasion.

scholarly journals Atoxigenic Aspergillus flavus Isolates Endemic to Almond, Fig, and Pistachio Orchards in California with Potential to Reduce Aflatoxin Contamination in these Crops

Plant Disease ◽  
2019 ◽  
Vol 103 (5) ◽  
pp. 905-912 ◽  
Author(s):  
Alejandro Ortega-Beltran ◽  
Juan Moral ◽  
Adeline Picot ◽  
Ryan D. Puckett ◽  
Peter J. Cotty ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Climatic Changes ◽  
Aflatoxin Contamination ◽  
Vegetative Compatibility ◽  
Export Markets ◽  
Tree Crops ◽  
Vegetative Compatibility Groups ◽  
Single Genotype ◽  
Aflatoxin Accumulation

In California, aflatoxin contamination of almond, fig, and pistachio has become a serious problem in recent years due to long periods of drought and probably other climatic changes. The atoxigenic biocontrol product Aspergillus flavus AF36 has been registered for use to limit aflatoxin contamination of pistachio since 2012 and for use in almond and fig since 2017. New biocontrol technologies employ multiple atoxigenic genotypes because those provide greater benefits than using a single genotype. Almond, fig, and pistachio industries would benefit from a multi-strain biocontrol technology for use in these three crops. Several A. flavus vegetative compatibility groups (VCGs) associated with almond, fig, and pistachio composed exclusively of atoxigenic isolates, including the VCG to which AF36 belongs to, YV36, were previously characterized in California. Here, we report additional VCGs associated with either two or all three crops. Representative isolates of 12 atoxigenic VCGs significantly (P < 0.001) reduced (>80%) aflatoxin accumulation in almond and pistachio when challenged with highly toxigenic isolates of A. flavus and A. parasiticus under laboratory conditions. Isolates of the evaluated VCGs, including AF36, constitute valuable endemic, well-adapted, and efficient germplasm to design a multi-crop, multi-strain biocontrol strategy for use in tree crops in California. Availability of such a strategy would favor long-term atoxigenic A. flavus communities across the affected areas of California, and this would result in securing domestic and export markets for the nut crop and fig farmer industries and, most importantly, health benefits to consumers.

scholarly journals Nutrient Environments Influence Competition among Aspergillus flavus Genotypes

2012 ◽  
Vol 79 (5) ◽  
pp. 1473-1480 ◽  
Author(s):  
Hillary L. Mehl ◽  
Peter J. Cotty
Keyword(s):  
Aspergillus Flavus ◽  
Mycelial Growth ◽  
Competitive Ability ◽  
Aflatoxin Contamination ◽  
Nucleotide Polymorphisms ◽  
Intraspecific Interactions ◽  
Single Nucleotide ◽  
Content Type ◽  
Agar Media ◽  
Nutrient Variability

ABSTRACTThe population dynamics ofAspergillus flavus, shaped in part by intraspecific competition, influence the likelihood and severity of crop aflatoxin contamination. Competition for nutrients may be one factor modulating intraspecific interactions, but the influences of specific types and concentrations of nutrients on competition between genotypes ofA. flavushave not been investigated. Competition between pairedA. flavusisolates on agar media was affected by varying concentrations of carbon (sucrose or asparagine) and nitrogen (nitrate or asparagine). Cocultivated isolate percentages from conidia and agar-embedded mycelia were quantified by measurements of isolate-specific single-nucleotide polymorphisms with quantitative pyrosequencing. Compositions and concentrations of nutrients influenced conidiation resulting from cocultivation, but the percentages of total conidia from each competing isolate were not predicted by sporulation of isolates grown individually. Success during sporulation did not reflect the outcomes of competition during mycelial growth, and the extents to which isolate percentages from conidia and mycelia differed varied among both isolate pairs and media. Whether varying concentrations of sucrose, nitrate, or asparagine increased, decreased, or had no influence on competitive ability was isolate dependent. Different responses ofA. flavusisolates to nutrient variability suggest genotypes are adapted to different nutrient environments that have the potential to influenceA. flavuspopulation structure and the epidemiology of aflatoxin contamination.

scholarly journals Identification of Atoxigenic Aspergillus flavus Isolates to Reduce Aflatoxin Contamination of Maize in Kenya

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 212-218 ◽  
Author(s):  
C. Probst ◽  
R. Bandyopadhyay ◽  
L. E. Price ◽  
P. J. Cotty
Keyword(s):  
Biological Control ◽  
Aspergillus Flavus ◽  
Aflatoxin Contamination ◽  
Fungal Communities ◽  
Management Tools ◽  
Maize Production ◽  
Vegetative Compatibility Groups ◽  
Potential Value ◽  
Maize Sample ◽  
Maize Kernels

Aspergillus flavus has two morphotypes, the S strain and the L strain, that differ in aflatoxin-producing ability and other characteristics. Fungal communities on maize dominated by the S strain of A. flavus have repeatedly been associated with acute aflatoxin poisonings in Kenya, where management tools to reduce aflatoxin levels in maize are needed urgently. A. flavus isolates (n = 290) originating from maize produced in Kenya and belonging to the L strain morphotype were tested for aflatoxin-producing potential. A total of 96 atoxigenic isolates was identified from four provinces sampled. The 96 atoxigenic isolates were placed into 53 vegetative compatibility groups (VCGs) through complementation of nitrate non-utilizing mutants. Isolates from each of 11 VCGs were obtained from more than one maize sample, isolates from 10 of the VCGs were detected in multiple districts, and isolates of four VCGs were found in multiple provinces. Atoxigenic isolates were tested for potential to reduce aflatoxin concentrations in viable maize kernels that were co-inoculated with highly toxigenic S strain isolates. The 12 most effective isolates reduced aflatoxin levels by >80%. Reductions in aflatoxin levels caused by the most effective Kenyan isolates were comparable with those achieved with a United States isolate (NRRL-21882) used commercially for aflatoxin management. This study identified atoxigenic isolates of A. flavus with potential value for biological control within highly toxic Aspergillus communities associated with maize production in Kenya. These atoxigenic isolates have potential value in mitigating aflatoxin outbreaks in Kenya, and should be evaluated under field conditions.

scholarly journals Identification of maize kernel resistance proteins against Aspergillus flavus by a statistical approach: A predictive model of resistance capacity.

Bionatura ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 1741-1750
Author(s):  
Leandro Balzano ◽  
Jesús Alezones ◽  
Nardy Diez García
Keyword(s):  
Aspergillus Flavus ◽  
Crop Production ◽  
Expression Profiles ◽  
Pathogen Resistance ◽  
Aflatoxin Contamination ◽  
Resistance Proteins ◽  
Kernel Infection ◽  
Protein Expression Profiles ◽  
Maize Kernels ◽  
Made In

Although kernel infection by Aspergillus flavus and pre-harvest aflatoxin contamination of Zea mays grain is a significant crop production problem, not only in Venezuela but also around the world, little progress has been made in identifying proteins and metabolic pathways associated with this pathogen resistance. Usually, a protein with a two-fold expression between control and condition is considered a biomarker of some phenomena, but we think it is essential to evaluate its contribution to resistance. That is why we decided to determine the behavior's resistance capacity in terms of expression levels of an identified protein of maize kernels infected with A. flavus by using a multivariate approach. In this work, we identify 47 of 66 differentially expressed spots with a remarkable contribution to resistance against the fungus Aspergillus flavus. We finally test this approach to know if it can be used as a predictive resistance model and probe it by including theoretical and experimental protein expression profiles of other inoculated maize lines.

scholarly journals In Vitro Activity of Balanites aegyptiaca and Tamarindus indica Fruit Extracts on Growth and Aflatoxigenicity of Aspergillus flavus and A. parasiticus

2013 ◽  
Vol 2 (4) ◽  
pp. 68 ◽  
Author(s):  
Saifeldin Ahmed El-nagerabi ◽  
Abdulkadir E. Elshafie ◽  
Mohamed R. Elamin
Keyword(s):  
Aspergillus Flavus ◽  
Fungal Growth ◽  
Aflatoxin Contamination ◽  
Tamarindus Indica ◽  
Balanites Aegyptiaca ◽  
Total Aflatoxin ◽  
Animal Products ◽  
Fruit Extracts ◽  
Aflatoxin B

<p>Aflatoxin and especially aflatoxin B<sub>1</sub> (AFB<sub>1</sub>) is a carcinogenic secondary metabolite synthesized by certain <em>Aspergillus </em>species. They contaminate natural and processed agricultural and animal products which render them unfit for consumption. The aim of this study was to evaluate the <em>in vitro</em> effects of <em>Balanites aegyptiaca</em> and <em>Tamarindus indica</em> fruit extracts on the growth and aflatoxin secretion of <em>Aspergillus flavus</em> (SQU21) and <em>A. parasiticus </em>(CBS921.7) strains. The two fruit extracts significantly (<em>P </em>&lt; 0.05) reduced aflatoxin and did not inhibit mycelial dry weights of the two <em>Aspergillus </em>strains. At different concentrations of balanites (2.5-10%), the inhibition of total aflatoxin was 49.9-84.8% for <em>A. flavus</em> (SQU21) and 32.1-84.4% for <em>A. parasiticus</em> (CBS921.7), whereas the inhibition of aflatoxin Bwas 38.2-81.4% and 32.8-80.6% for the two strains. Tamarind fruit extract (2.5-7.5%) caused 28.8-84.2% and 40.7-85.5% reductions in total aflatoxin and 37.1-83.5% and 33.9-85.9% in aflatoxin B for the two strains, respectively. None of these extracts inhibited the fungal growth or detoxified synthetic aflatoxin B<sub>1</sub>. We have concluded that these fruits contain various inhibitors to aflatoxin biosynthesis and secretion. Therefore, they can be used in combination as safe green biopreservatives to combat aflatoxin contamination of food.</p>

Living Maize Embryo Influences Accumulation of Aflatoxin in Maize Kernels

1993 ◽  
Vol 56 (11) ◽  
pp. 967-971 ◽  
Author(s):  
ROBERT L. BROWN ◽  
PETER J. COTTY ◽  
THOMAS E. CLEVELAND ◽  
NEIL W. WIDSTROM
Keyword(s):  
Aspergillus Flavus ◽  
Fungal Growth ◽  
Aflatoxin Contamination ◽  
Population Variation ◽  
Maize Populations ◽  
Susceptible Control ◽  
Maize Embryo ◽  
Metabolic Activities ◽  
Maize Kernels ◽  
Two Populations

Kernels from two maize populations, MAS:gk and MAS:pw,nf, showed significant postharvest resistance to aflatoxin contamination by Aspergillus flavus but showed no significant inter-population variation for this resistance. Growth of A. flavus on both populations was significantly less than on susceptible control lines. Kernels from the resistant populations retained resistance when wounded through the pericarp prior to inoculation with A. flavus, despite the fact that the exposed endosperm supported good fungal growth. Kernels from these populations also retained resistance when they were acetone washed before inoculation. Resistance to aflatoxin contamination was lost in kernels that were autoclaved, crushed, or embryo wounded. All assays were incubated under conditions favorable to kernel germination. Results suggest that postharvest resistance to aflatoxin contamination in these two populations is related to metabolic activities of the living com embryo.

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