Spatial and temporal population dynamics of Aspergillus flavus in commercial pistachio orchards in Arizona

2022 ◽  
Author(s):  
Connel Ching'anda ◽  
Joseph Atehnkeng ◽  
Ranajit Bandyopadhyay ◽  
Kenneth Callicott ◽  
Marc J Orbach ◽  
...  
Keyword(s):  
Population Dynamics ◽  
High Temperature ◽  
Aspergillus Flavus ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Tree Nut ◽  
Wide Range ◽  
Tree Canopies ◽  
Biocontrol Strain

Aspergillus flavus infects a wide range of crops, including pistachios, and subsequent aflatoxin contamination results in significant economic losses. Application of biocontrol products based on non-aflatoxigenic (atoxigenic) strains of A. flavus is one of the most effective tactics for controlling aflatoxins in crops. Both risk of aflatoxin contamination and effectiveness of biocontrol are influenced by the extent to which A. flavus spores move into pistachio tree canopies during periods of nut development. Thus, the purpose of this study was to evaluate spatial and temporal population dynamics of A. flavus, including the applied biocontrol strain AF36, in canopies of pistachio orchards in Arizona. Propagule densities of A. flavus were quantified on leaf samples collected from lower, middle, and upper canopies from spring through harvest in 2018 and 2019. Aspergillus flavus propagule densities peaked during periods of high temperature and rainfall in 2018 (up to 600 CFU/g) and 2019 (up to 23 CFU/g), which coincided with nut development and maturation. The applied biocontrol strain AF36 was detected at all canopy heights, but overall propagule densities were greater in the upper and middle canopy (mean = 70 CFU/g) compared to the lower canopy (mean = 47 CFU/g). Results suggest June to August is the period during which A. flavus inoculum increases in Arizona pistachio orchards, and to most effectively displace aflatoxin-producing fungi in tree canopies, biocontrol applications should precede this period. In addition, this study demonstrates that soil-applied biocontrol strains can successfully disperse throughout the canopies of commercial tree nut orchards.

Quantification of the aflatoxin biocontrol strain Aspergillus flavus AF36 in soil, and nuts and leaves of pistachio by real-time PCR

Plant Disease ◽  
2020 ◽  
Author(s):  
MARÍA TERESA GARCÍA LOPEZ ◽  
Yong Luo ◽  
Alejandro Ortega-Beltran ◽  
Ramon Jaime ◽  
Juan Moral Moral ◽  
...  
Keyword(s):  
Real Time ◽  
Aspergillus Flavus ◽  
Real Time Pcr ◽  
Management Strategies ◽  
Cost Savings ◽  
Aflatoxin Contamination ◽  
Conidial Suspension ◽  
Toxigenic Strains ◽  
Important Time ◽  
Biocontrol Strain

The species Aspergillus flavus and A. parasiticus are commonly found in the soils of nut-growing areas in California. Several isolates can produce aflatoxins that occasionally contaminate nut kernels conditioning their sale. The strain AF36 of A. flavus, which does not produce aflatoxins, is registered as a biocontrol agent for use in almond, pistachio, and fig crops in California. After application in the orchards, AF36 displaces aflatoxin-producing Aspergillus spp. and thus reduces aflatoxin contamination. Vegetative compatibility assays (VCA) have traditionally been used to track AF36 in soils and crops where it has been applied. However, VCA is labor-intensive and time-consuming. Here, we developed a quantitative real-time PCR (qPCR) protocol to quantify proportions of AF36 accurately and efficiently in different substrates. Specific primers to target AF36 and toxigenic strains of A. flavus and A. parasiticus were designed based on sequence of aflC, a gene essential for aflatoxin biosynthesis. Standard curves were generated to calculate proportions of AF36 based on threshold values (Cq). Verification assays using pure DNA and conidial suspension mixtures demonstrated a significant relationship by regression analysis between known and qPCR-measured AF36 proportions in DNA (R2 = 0.974; P < 0.001) and conidia mixtures (R2 = 0.950; P < 0.001). The tests conducted by qPCR in pistachio leaves, nuts, and soil samples demonstrated the usefulness of the qPCR method to precisely quantify proportions of AF36 in diverse substrates, ensuring important time and cost savings. The outputs of the current study will serve to design better aflatoxin management strategies for pistachio and other crops.

Spatial variability of Aspergillus flavus soil populations under different crops and corn grain colonization and aflatoxins

2004 ◽  
Vol 82 (12) ◽  
pp. 1768-1775 ◽  
Author(s):  
H K Abbas ◽  
R M Zablotowicz ◽  
M A Locke
Keyword(s):  
Zea Mays ◽  
Spatial Structure ◽  
Spatial Variability ◽  
Aspergillus Flavus ◽  
Mississippi Delta ◽  
Aflatoxin Production ◽  
Aflatoxin Contamination ◽  
Moderate Degree ◽  
Wide Range ◽  
Corn Kernels

Aflatoxin contamination in corn caused by Aspergillus flavus Link is a serious constraint on economical corn (Zea mays L.) production in the Mississippi Delta. The ecology of A. flavus was evaluated in a 3-year study assessing the spatial variability of soil populations of A. flavus in a Mississippi Delta field under different crops. A 1.07-ha section of the field was laid out in 126 9.2-m2 plots, and soil was sampled in May 2000, March 2001, and April 2002. Aspergillus flavus populations were determined by plating on selective media, and A. flavus colonization was assessed in corn during 2000. Aspergillus flavus populations in soil were significantly (P < 0.01 level) influenced by previous crop. The highest propagule density (794 cfu·g–1) was found following the corn crop in 2001 versus 251 cfu·g–1 soil in 2000 following cotton and 457 cfu·g–1 following wheat in 2002. Aspergillus flavus populations in 2001 and 2002 exhibited a moderate degree of spatial structure, described by spherical and exponential models, respectively, but populations in 2000 exhibited little spatial structure. Colonization of corn kernels by A. flavus in 2000 ranged from 0% to 100% (mean = 15% colonized kernels), and aflatoxin levels ranged from 0 to 1590 ppb (mean = 57 ppb). Aflatoxin levels were randomly distributed in the field and not correlated with A. flavus colonization. Aflatoxin production was found in 43% to 59% of A. flavus soil isolates with the highest incidence in soil populations following corn in 2001. However, 84% of A. flavus isolated from corn kernels produced aflatoxin. Results indicate that within a single field there was a wide range of A. flavus soil propagule densities varying in potential to produce aflatoxin.Key words: Aspergillus flavus, aflatoxins, soil, corn (Zea mays), cotton, wheat, spatial variability.

scholarly journals Transcriptional Regulation of Aflatoxin Biosynthesis and Conidiation in Aspergillus flavus by Wickerhamomyces anomalus WRL-076 for Reduction of Aflatoxin Contamination

Toxins ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 81 ◽  
Author(s):  
Sui Hua ◽  
Siov Sarreal ◽  
Perng-Kuang Chang ◽  
Jiujiang Yu
Keyword(s):  
Aspergillus Flavus ◽  
Molecular Mechanisms ◽  
Field Experiments ◽  
Regulatory Gene ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Expression Levels ◽  
Wickerhamomyces Anomalus ◽  
Cultural Medium ◽  
Major Producer

Aspergillus flavus is a ubiquitous saprophytic fungus found in soils across the world. The fungus is the major producer of aflatoxin (AF) B1, which is toxic and a potent carcinogen to humans. Aflatoxin B1 (AFB1) is often detected in agricultural crops such as corn, peanut, almond, and pistachio. It is a serious and recurrent problem and causes substantial economic losses. Wickerhamomyces anomalus WRL-076 was identified as an effective biocontrol yeast against A. flavus. In this study, the associated molecular mechanisms of biocontrol were investigated. We found that the expression levels of eight genes, aflR, aflJ, norA, omtA, omtB, pksA, vbs, and ver-1 in the aflatoxin biosynthetic pathway cluster were suppressed. The decreases ranged from several to 10,000 fold in fungal samples co-cultured with W. anomalus. Expression levels of conidiation regulatory genes brlA, abaA, and wetA as well as sclerotial regulatory gene (sclR) were all down regulated. Consistent with the decreased gene expression levels, aflatoxin concentrations in cultural medium were reduced to barely detectable. Furthermore, fungal biomass and conidial number were significantly reduced by 60% and more than 95%, respectively. The results validate the biocontrol efficacy of W. anomalus WRL-076 observed in the field experiments.

scholarly journals Distribution, Genetic Diversity and Biocontrol of Aflatoxigenic Aspergillus flavus in Serbian Maize Fields

Toxins ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 687
Author(s):  
Vanja Vlajkov ◽  
Mila Grahovac ◽  
Dragana Budakov ◽  
Marta Loc ◽  
Ivana Pajčin ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
High Performance ◽  
Critical Role ◽  
High Capacity ◽  
Aflatoxin Production ◽  
Elisa Test ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Enzyme Linked Immunosorbent Assay ◽  
The Republic

Maize is one of the leading export products in the Republic of Serbia. As a country where economic development depends on agriculture, maize production plays a critical role as a crop of strategic importance. Potential aflatoxin contamination of maize poses a risk to food and feed safety and tremendous economic losses. No aflatoxin contamination of maize samples harvested in 2019 and 2020 in different localities in the Republic of Serbia was detected by the Enzyme-Linked Immunosorbent Assay (ELISA) test and High-Performance Liquid Chromatography (HPLC) method. On the other hand, the Cluster Amplification Patterns (CAP) analyses of the isolated Aspergillus flavus strains from 2019 maize samples confirmed the presence of key biosynthesis genes responsible for aflatoxin production. Artificial inoculation and subsequent HPLC analysis of the inoculated maize samples confirmed the high capacity of the A. flavus strains for aflatoxin production, pointing to a high risk of contamination under favorable conditions. Prevention of aflatoxin contamination is primarily based on A. flavus control, where biocontrol agents play a significant role as sustainable disease management tools. In this study, antagonistic activity screening of the novel strains belonging to the Bacillus genus indicated superior suppression of A. flavus strains by two Bacillus strains isolated from the rhizosphere of Phaseolus vulgaris.

Resistance to Aspergillus flavus and A. parasiticus in almond advanced selections and cultivars and its interaction with the aflatoxins biocontrol strategy

Plant Disease ◽  
2021 ◽  
Author(s):  
Juan Moral Moral ◽  
MARÍA TERESA GARCÍA LOPEZ ◽  
Ana Gordon ◽  
Alejandro Ortega-Beltran ◽  
Ryan D Puckett ◽  
...  
Keyword(s):  
Biological Control ◽  
Aspergillus Flavus ◽  
Aflatoxin Contamination ◽  
Protective Effects ◽  
Control Strain ◽  
Cultivar Resistance ◽  
Global Leader ◽  
Traditional Cultivars ◽  
Almond Cultivar ◽  
Biocontrol Strain

Aflatoxin contamination of almond kernels, caused by Aspergillus flavus and A. parasiticus, is a severe concern for growers due to its high toxicity. In California, the global leader of almond production, aflatoxin can be managed by applying the biological control strain AF36 of A. flavus and selecting resistant cultivars. Here, we classified the almond genotypes by K-Means cluster analysis into three groups [Susceptible (S), Moderately Susceptible (MS), or Resistant (R)] based on aflatoxin content of inoculated kernels. The protective effects of the shell and seedcoat in preventing aflatoxin contamination were also examined. The presence of intact shells reduced aflatoxin contamination over 100-fold. The seedcoat provided a layer of protection, but not complete. In kernel inoculation assays, none of the studied almond genotypes showed a total resistance to the pathogen. However, nine traditional cultivars and four advanced selections were classified as R. Because these advanced selections contained germplasm derived from peach, we compared the kernel resistance of three peach cultivars to that shown by kernels of a R (‘Sonora’) and a S (‘Carmel’) almond cultivar and five pistachio cultivars. Overall, peach kernels were significantly more resistant to the pathogen than almond kernels, which were more resistant than pistachio kernels. Finally, we studied the combined effect of the cultivar resistance and the biocontrol strain AF36 in limiting aflatoxin contamination. For this, we co-inoculated almond kernels of R ‘Sonora’ and S ‘Carmel’ with AF36 72 h before or 48 h after inoculating with an aflatoxin-producing strain of A. flavus. The percentage of aflatoxin reduction by AF36 strain was greater in kernels of ‘Carmel’ kernels (98%) than in those of ‘Sonora’ (83%). Cultivar resistance also affected the kernel colonization by the biological control strain. AF36 strain limited aflatoxin contamination in almond kernels even when applied 48 h after the aflatoxin-producing strain. Our results show that biocontrol combined with the use of cultivars with resistance to aflatoxin contamination can result in a more robust protection strategy than the use of either practices in isolation.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

PLATINUM

Alloy Digest ◽  
1970 ◽  
Vol 19 (11) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Heat Treating ◽  
Industrial Applications ◽  
High Melting ◽  
High Melting Point ◽  
White Metal ◽  
Temperature Performance ◽  
Wide Range ◽  
Corrosion And Oxidation

Abstract PLATINUM is a soft, ductile, white metal which can be readily worked either hot or cold. It has a wide range of industrial applications because of its excellent corrosion and oxidation resistance and its high melting point. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Pt-1. Producer or source: Matthey Bishop Inc..

ACI TYPE HN

Alloy Digest ◽  
1982 ◽  
Vol 31 (6) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Steel Casting ◽  
Nickel Content ◽  
Heat Treating ◽  
High Temperature Corrosion ◽  
Temperature Performance ◽  
Wide Range ◽  
Iron Chromium

Abstract Type HN is an iron-chromium-nickel alloy containing sufficient chromium for good high-temperature corrosion resistance and with nickel content in excess of the chromium. This alloy has properties somewhat similar to the more widely used ACI Type HT alloy but with better ductility. Type HN is used for highly stressed components in the 1800-2000 F temperature range. It is used in the aircraft, automotive, petroleum, petrochemical and power industries for a wide range of components and parts. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: SS-410. Producer or source: Various stainless steel casting companies.

scholarly journals Toxin Production in Soybean (Glycine max L.) Plants with Charcoal Rot Disease and by Macrophomina phaseolina, the Fungus that Causes the Disease

Toxins ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 645 ◽  
Author(s):  
Hamed K. Abbas ◽  
Nacer Bellaloui ◽  
Cesare Accinelli ◽  
James R. Smith ◽  
W. Thomas Shier
Keyword(s):  
Culture Media ◽  
Leaf Disc ◽  
Toxin Production ◽  
Macrophomina Phaseolina ◽  
Economic Losses ◽  
Limit Of Quantification ◽  
Charcoal Rot ◽  
Wide Range ◽  
Soybean Plants ◽  
Rot Disease

Charcoal rot disease, caused by the fungus Macrophomina phaseolina, results in major economic losses in soybean production in southern USA. M. phaseolina has been proposed to use the toxin (-)-botryodiplodin in its root infection mechanism to create a necrotic zone in root tissue through which fungal hyphae can readily enter the plant. The majority (51.4%) of M. phaseolina isolates from plants with charcoal rot disease produced a wide range of (-)-botryodiplodin concentrations in a culture medium (0.14–6.11 µg/mL), 37.8% produced traces below the limit of quantification (0.01 µg/mL), and 10.8% produced no detectable (-)-botryodiplodin. Some culture media with traces or no (-)-botryodiplodin were nevertheless strongly phytotoxic in soybean leaf disc cultures, consistent with the production of another unidentified toxin(s). Widely ranging (-)-botryodiplodin levels (traces to 3.14 µg/g) were also observed in the roots, but not in the aerial parts, of soybean plants naturally infected with charcoal rot disease. This is the first report of (-)-botryodiplodin in plant tissues naturally infected with charcoal rot disease. No phaseolinone was detected in M. phaseolina culture media or naturally infected soybean tissues. These results are consistent with (-)-botryodiplodin playing a role in the pathology of some, but not all, M. phaseolina isolates from soybeans with charcoal rot disease in southern USA.

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