scholarly journals Development of an ELISA-Based Method for Testing Aflatoxigenicity and Aflatoxigenic Variability among Aspergillus species in Culture

2019 ◽  
Author(s):  
Lagat Kipkemboi Micah ◽  
Faith Jebet Toroitich ◽  
Meshack Amos Obonyo
Keyword(s):  
Biological Control ◽  
Aflatoxin Production ◽  
Toxin Production ◽  
Field Trials ◽  
Control Programs ◽  
Color Changes ◽  
Visual Color ◽  
Aflatoxigenic Fungi ◽  
Maize Kernels ◽  
First Time

AbstractAflatoxins contaminate foodstuff posing a severe threat to human health because chronic exposure is linked to liver cancer while acute exposure may cause death. Therefore, it is of interest to reduce the contamination of crops by aflatoxins in the field and post-harvest. Among the current technologies being developed is the deployment of non-aflatoxigenic strains of Aspergillus species to competitively exclude aflatoxigenic conspecifics from crops in the field thereby curtailing aflatoxin production by the former. The success in this endeavor makes the non-aflatoxigenic fungi good candidates for biological control programs. However, the current techniques for segregating non-aflatoxigenic from aflatoxigenic fungi suffer two main drawbacks: they are based on morphological and chemical tests with a combination of visual color changes detected in a culture plate which suffer some degree of inaccuracy. Secondly, the existing methods are incapable of accurately quantifying aflatoxin production by fungi in culture. We developed a culture system for inducing aflatoxin production by Aspergillus using maize kernels as growth substrate followed by quantification using ELISA. The method was compared to the Dichlorvos-Ammonia (DV-AM) method for determining aflatoxigenicity. Our findings encapsulate a method more robust than the currently used DV-AM approach because, for the first time, we are able to assess aflatoxigenicity and aflatoxigenic variability among Aspergillus species earlier classified as non-aflatoxigenic by the DV-AM method. Furthermore, the new method presents an opportunity to attribute toxin production by actively growing fungal cultures. We believe this method when further developed presents a chance to study and predict fungal behavior prior to field trials for biological control programs.

scholarly journals Genetic and chemical methods of ascertaining aflatoxigenicity give discordant results: A Case of Aspergillus species from Eastern Kenya

2021 ◽  
Author(s):  
Micah Kipkemboi Lagat ◽  
Faith Jebet Toroitich ◽  
Huxley Mae Makonde ◽  
Meshack Amos Obonyo
Keyword(s):  
Internal Transcribed Spacer ◽  
Chemical Method ◽  
Its Region ◽  
Aflatoxin Production ◽  
Toxin Production ◽  
Epigenetic Factors ◽  
Chemical Methods ◽  
Control Programs ◽  
Genetic Abundance ◽  
Maize Kernels

Abstract Background: Aflatoxins (AFs) are poisonous compounds produced by species of fungi belonging to the genus Aspergillus mainly A. flavus and A. parasiticus. However, there are some members of these species that do not produce toxins and have since become of interest for use in Biological Control programs. The species that produce AFs are believed to have clusters of aflatoxin-associated genes that confer aflatoxigenicity. However, recent findings suggest that the presence of aflatoxin genes may not imply aflatoxin production capability. We therefore examined the extent to which the presence or absence of aflatoxin-associated genes (genetic) infers aflatoxigenicity using the Dichlorvos-Ammonia (chemical) method as reference.Results: We report a dissonance between the genetic and chemical methods of ascertaining aflatoxigenicity. Fungi (n = 314) that were morphologically identified as A. flavus and A. parasiticus were isolated from maize kernels and soil from Eastern Kenya. The fungi were further characterized to confirm their identities using a PCR-sequence analysis of the internal transcribed spacer (ITS) region of rDNA which confirmed them to be Aspergillus species. We selected and induced 16 isolates in YES media amended with Dichlorvos to produce AFs. Seven of the sixteen isolates were DM-AM positive (aflatoxigenic) but lacked at least one of the key aflatoxin-associated genes. Even more confounding, A. flavus isolate (1EM2606) had all aflatoxin-associated genes but was non-aflatoxigenic (DV-AM negative) while A. flavus (1EM1901) having all genes was aflatoxigenic (DV-AM positive). The genetic abundance of the AF-asscociated genes among the isolates was as follows: aflQ (100%), aflD (62.5%) followed by aflR (37.5%) and aflP (25%). Conclusion: We report that either method alone is limited in ascertaining aflatoxigenicity among Aspergillus section Flavi. The discordance between presence of aflatoxin-associated genes and aflatoxigenicity may be due to epigenetic factors that affect secondary metabolism, or even other signaling processes that alter toxin production that still remain poorly understood.

scholarly journals Biological Control of Tephritid Fruit Flies in the Americas and Hawaii: A Review of the Use of Parasitoids and Predators

Insects ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 662
Author(s):  
Flávio R. M. Garcia ◽  
Sérgio M. Ovruski ◽  
Lorena Suárez ◽  
Jorge Cancino ◽  
Oscar E. Liburd
Keyword(s):  
Biological Control ◽  
Fruit Fly ◽  
Fruit Flies ◽  
Economic Importance ◽  
Parasitoid Species ◽  
Control Programs ◽  
First Time ◽  
Tephritid Fruit Flies

Biological control has been the most commonly researched control tactic within fruit fly management programs. For the first time, a review is carried out covering parasitoids and predators of fruit flies (Tephritidae) from the Americas and Hawaii, presenting the main biological control programs in this region. In this work, 31 species of fruit flies of economic importance are considered in the genera Anastrepha (11), Rhagoletis (14), Bactrocera (4), Ceratitis (1), and Zeugodacus (1). In this study, a total of 79 parasitoid species of fruit flies of economic importance are listed and, from these, 50 are native and 29 are introduced. A total of 56 species of fruit fly predators occur in the Americas and Hawaii.

scholarly journals Natural enemies of armored scales (Hemiptera: Diaspididae) and soft scales (Hemiptera: Coccoidae) in Chile: molecular and morphological identification

2018 ◽  
Author(s):  
P. Amouroux ◽  
D. Crochard ◽  
M.C.G. Correa ◽  
G. Groussier ◽  
P. Kreiter ◽  
...  
Keyword(s):  
Biological Control ◽  
Natural Enemies ◽  
Ornamental Plants ◽  
Integrative Taxonomy ◽  
Scale Insects ◽  
Morphological Identification ◽  
Correct Identification ◽  
Predator Species ◽  
Control Programs ◽  
First Time

AbstractScale insects (Hemiptera: Coccoidea) are key pests of agricultural crops and ornamental plants worldwide. Their populations are difficult to control, even with insecticides, due to their cryptic habits. Moreover, there is growing concern over the use of synthetic pesticides for their control, due to deleterious environmental effects and the emergence of resistant populations of target pests. In this context, biological control may be an effective and sustainable approach. Hymenoptera Chalcidoidea includes natural enemies of scale insects that have been successfully used in many biological control programs. However, the correct identification of pest scale species and their natural enemies is particularly challenging because these insects are very small and highly specialized. Integrative taxonomy, coupling DNA barcoding and morphological analysis, has been successfully used to characterize pests and natural enemy species. In this study, we performed a survey of parasitoids and predators of armored and soft scales in Chile, based on 28S and COI barcodes. Fifty-three populations of Diaspididae and 79 populations of Coccidae were sampled over the entire length of the country, from Arica (18°S) to Frutillar (41°S), between January 2015 and February 2016. The phylogenetic relationships obtained by Bayesian inference from multilocus haplotypes revealed 40 putative species of Chalcidoidea, five Coccinellidae and three Neuroptera. In Chalcidoidea, 22 species were identified morphologically, resulting in new COI barcodes for 12 species and new 28S barcodes for 14 species. Two predator species (Rhyzobius lophantae and Coccidophilus transandinus) were identified morphologically, and two parasitoid species, Chartocerus niger and Signiphora bifasciata, were recorded for the first time in Chile.

scholarly journals Report of A Larval Parasitoid of Tuta Absoluta (Meyrick) (Lepidoptera: Gelechiidae) from Iran

2014 ◽  
Vol 54 (3) ◽  
pp. 306-307 ◽  
Author(s):  
Fariba Sohrabi ◽  
Hossein Lotfalizadeh ◽  
Hoda Salehipour
Keyword(s):  
Biological Control ◽  
Natural Enemies ◽  
Tuta Absoluta ◽  
Parasitoid Species ◽  
Tomato Leafminer ◽  
Control Programs ◽  
Larval Parasitoid ◽  
The Family ◽  
Introduced Pest ◽  
First Time

Abstract The tomato leafminer Tuta absoluta (Meyrick) is one of the most devastating pests of greenhouse and outdoor tomato crops. Since it is a newly introduced pest in Iran, there is an important need to search for its natural enemies. In the course of a survey on the natural enemies of this pest, samplings were carried out in tomato greenhouses heavily infested with the tomato leafminer, in the Borazjan region of the Bushehr province in Iran. Leaves with mines were reared in the laboratory until emergence of parasitoids. A single parasitoid species of the family Eulophidae was reared and identified as Neochrysocharis formosus (Westwood 1833). This species is reported for the first time on the tomato leafminer in Iran. Such information may help in developing biological control programs to control this serious pest.

scholarly journals Genetic variability among three Egyptian isolates of Heterorhabditis indica using a new marker technique (SCoT)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Amany M. Abd El Azim ◽  
Etr H. K. Khashaba
Keyword(s):  
Biological Control ◽  
Agricultural Soils ◽  
Insect Pests ◽  
Genetic Relationships ◽  
Its Region ◽  
Start Codon ◽  
Heterorhabditis Indica ◽  
Control Programs ◽  
Scot Marker ◽  
First Time

Abstract Background Entomopathogenic nematodes (EPNs) are a group of nematode families, have the ability to search for their hosts, and are considered as promising biological control candidates for insect pests, providing protection to non-target organisms and the environment. Results This study was conducted to isolate indigenous EPN isolates from Egyptian agricultural soils for further use in biological control programs and study their genetic polymorphism among the previously isolated isolates under accession no. MH553167 and MK300683 and the new isolate (MH496627), using the start codon targeted (SCoT) marker. One out of 15 soil samples obtained from a banana cultivated field was positive for the presence of EPNs, using the Galleria baiting method. Morphological analysis and sequencing of the internal transcribed spacer (ITS) region suggested that the isolate obtained belongs to Heterorhabditis indica. The sequence of the ITS was submitted to the National Center for Biotechnology Information (NCBI) and registered under accession no. MH496627. Ten SCoT primers were used in the study; the polymorphic bands were 68 out of 76 with 89% as polymorphism percentage. The highest numbers of bands were 10 bands generated by SCoT 1 and SCoT 18 while SCoT 48 and SCoT 60 recorded the lowest band number (5 bands). Conclusions The present study is considered as a preliminary study to demonstrate the effectiveness of the SCoT marker for the first time in assessing genetic relationships in EPNs.

scholarly journals Incidence of Mythimna sequax parasitized in wheat crop

2015 ◽  
Vol 45 (12) ◽  
pp. 2121-2124 ◽  
Author(s):  
Orcial Ceolin Bortolotto ◽  
Ayres de Oliveira Menezes Júnior ◽  
Adriano Thibes Hoshino ◽  
Geraldo Salgado-Neto
Keyword(s):  
Biological Control ◽  
Wheat Crop ◽  
Crop Season ◽  
Control Programs ◽  
Lespesia Archippivora ◽  
First Time ◽  
Natural Parasitism

ABSTRACT: This study investigated the natural parasitism of Mythimna sequax Franclemont, 1951, in wheat during the crop season of 2008. In total, 237 larvae were captured, of which 10.12% were parasitized. The Tachinidae species Winthemia trinitatis (Thompson, 1963), Winthemia tricolor (Wulp, 1890), Lespesia aletiae (Riley, 1879), and Lespesia archippivora Beneway, 1963 are reported for the first time parasitizing the wheat armyworm in Brazil. In addition, two other genus of parasitoids were identified, one Tachinidae Peleteria Robineau-Desvoidy, 1830 and one Ichneumonidae Ophion (Fabricius, 1798). This study reported for the first time four Tachinidae species parasitizing W. sequax, and further studies are needed to promote the conservation of these parasitoids in agroecossystem and development biological control programs for management of the wheat armyworm.

ChemInform Abstract: Aflastatin A, a Novel Inhibitor of Aflatoxin Production by Aflatoxigenic Fungi.

ChemInform ◽  
2010 ◽  
Vol 28 (30) ◽  
pp. no-no
Author(s):  
M. ONO ◽  
S. SAKUDA ◽  
A. SUZUKI ◽  
A. ISOGAI
Keyword(s):  
Aflatoxin Production ◽  
Aflatoxigenic Fungi

Evaluation of pruning wound protection products for the management of almond canker diseases in California

Plant Disease ◽  
2021 ◽  
Author(s):  
Leslie Amanda Holland ◽  
Renaud Travadon ◽  
Daniel P. Lawrence ◽  
Mohamed Taieb Nouri ◽  
Florent P Trouillas
Keyword(s):  
Biological Control ◽  
Fungal Pathogens ◽  
Tree Mortality ◽  
Biological Control Agent ◽  
Field Trials ◽  
Control Agent ◽  
Thiophanate Methyl ◽  
Pruning Wound ◽  
Wound Protection ◽  
Canker Pathogens

Almond trunk and branch canker diseases constitute a major cause of tree mortality in California. Numerous fungal pathogens have been associated with these canker diseases and pruning wounds act as major infection courts. Prior to this study, there were no products registered in California for the management of these diseases. In this study, fungicidal products including synthetic chemistries, biocontrols, paint and a sealant were evaluated for preventing fungal pathogen infection via pruning wounds. In four field trials conducted over two dormant seasons, sixteen pruning wound treatments were tested using hand-held spray applications, against five almond canker pathogens, namely Botryosphaeria dothidea, Neofusicoccum parvum, Cytospora sorbicola, Ceratocystis destructans, and Eutypa lata. The fungicide thiophanate-methyl (Topsin M) provided 82% overall disease prevention against four fungal pathogens. The biological control agent, Trichoderma atroviride SC1 (Vintec), tested at three application rates, resulted in 90 to 93% protection of pruning wounds in field trials, and for individual pathogens ranged from 81-100% protection for the three rates. At the time of this publication, Vintec is being considered for registration as a biological control product for the prevention of almond canker diseases, while Topsin M is recommended to growers for the prevention of almond canker diseases. This research indicates that effective protection of pruning wounds from infection by almond canker pathogens can be achieved with a one-time spray application of thiophanate-methyl or the biocontrol, T. atroviride SC1 (recommended 2 g/liter) after pruning.

scholarly journals Mechanistically Compatible Mixtures of Bacterial Antagonists Improve Biological Control of Fire Blight of Pear

2011 ◽  
Vol 101 (1) ◽  
pp. 113-123 ◽  
Author(s):  
V. O. Stockwell ◽  
K. B. Johnson ◽  
D. Sugar ◽  
J. E. Loper
Keyword(s):  
Biological Control ◽  
Plant Disease ◽  
Fire Blight ◽  
Biological Control Agent ◽  
Field Trials ◽  
Control Agent ◽  
Extracellular Protease ◽  
Peptide Antibiotics ◽  
Biological Control Agents ◽  
Control Activity

Mixtures of biological control agents can be superior to individual agents in suppressing plant disease, providing enhanced efficacy and reliability from field to field relative to single biocontrol strains. Nonetheless, the efficacy of combinations of Pseudomonas fluorescens A506, a commercial biological control agent for fire blight of pear, and Pantoea vagans strain C9-1 or Pantoea agglomerans strain Eh252 rarely exceeds that of individual strains. A506 suppresses growth of the pathogen on floral colonization and infection sites through preemptive exclusion. C9-1 and Eh252 produce peptide antibiotics that contribute to disease control. In culture, A506 produces an extracellular protease that degrades the peptide antibiotics of C9-1 and Eh252. We hypothesized that strain A506 diminishes the biological control activity of C9-1 and Eh252, thereby reducing the efficacy of biocontrol mixtures. This hypothesis was tested in five replicated field trials comparing biological control of fire blight using strain A506 and A506 aprX::Tn5, an extracellular protease-deficient mutant, as individuals and combined with C9-1 or Eh252. On average, mixtures containing A506 aprX::Tn5 were superior to those containing the wild-type strain, confirming that the extracellular protease of A506 diminished the biological control activity of C9-1 and Eh252 in situ. Mixtures of A506 aprX::Tn5 and C9-1 or Eh252 were superior to oxytetracycline or single biocontrol strains in suppressing fire blight of pear. These experiments demonstrate that certain biological control agents are mechanistically incompatible, in that one strain interferes with the mechanism by which a second strain suppresses plant disease. Mixtures composed of mechanistically compatible strains of biological control agents can suppress disease more effectively than individual biological control agents.

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