Aims: Dendrobiums are majorly affected by Fusarium proliferatum and F. oxysporum. The aim of this research was to utilise the mycotoxin, fusaric acid (FA) on Dendrobium hybrid to produce cultivars that are resistant towards these fungi. Methodology and results: FA of concentrations 0.05, 0.10, 0.15 and 0.20 mM were transferred to sterilised halfstrength Murashige and Skoog (MS) medium and inoculated with four weeks old thin cell layer (TCL) of protocorm-like bodies (PLBs) for eight weeks. It was deduced that PLBs treated with 0.10 mM of FA resulted in highest survival and shoot regeneration rate but the survival and regeneration rate began to decline as the concentrations of FA were increased. Histology and scanning electron microscopy (SEM) observation showed prominent cell damage and stomatal closure in PLBs treated with FA. Direct amplification of minisatellite DNA (DAMD) markers showed polymorphism in the FA treated PLBs compared to the control PLBs. In the leaf bridge bioassay, plantlets treated with 0.05 mM of FA showed most resistance towards both fungal species. Conclusion, significance and impact of study: Therefore, this research is a preliminary screening study where the optimum concentration of FA was selected based on the reaction of treated TCL of PLBs towards these mutagens.
Aims: Groundnut is an important food crop and is susceptible to contamination by Aspergillus. The present study was conducted to identify Aspergillus spp. from groundnuts as well as to detect mycotoxin production by toxigenic species. Methodology and results: Molecular identification using ITS region, β-tubulin and calmodulin genes identified six species, A. niger, A. tubingensis, A. flavus, A. aculeatus, A. sydowii and A. fumigatus. Phylogenetic tree of combined sequences showed the isolates from the same species were grouped with reference strains in the same clade, thus the species identity was confirmed. Detection of mycotoxin biosynthesis genes can give an indication of mycotoxin production. Two ochratoxin A genes, PKS15KS and PKS15C-MeT were detected in seven A. niger isolates but none of the isolates produced ochratoxin A when quantification was conducted using Ultra-High Performance Liquid Chromatography. Two aflatoxin B1 biosynthesis genes, Nor-1 (norsolorinic acid) and Ver-1 (Versicolorin) genes were detected in A. flavus but only KDH7 and KL27b isolates produced aflatoxin B1 with concentrations of 1.0 μg/g and 1.1 μg/g, respectively. Conclusion, significance and impact of the study: Various species of Aspergillus found on groundnuts may lead to potential mycotoxin contamination as toxigenic species were also recovered. The occurrence of Aspergillus spp. can reduce the quality of the legumes as well as reducing their shelf life.
Aims: Xerophilic Aspergillus spp. promote the growth of toxigenic species. Since mycotoxins are toxic to human and animal, identification of these species is important. Methodology and results: Two xerophilic species isolated from peanuts (Arachis hypogaea) were identified based on morphological characteristics, molecular identification, and phylogenetic analysis using internal transcribed spacer region, β-tubulin, and calmodulin sequences. Conclusion, significance and impact of study: The occurrence of A. chevalieri and A. amstelodami on peanuts provides favorable growth conditions for less xerophilic Aspergillus as well as other spoilage-related fungal genera, particularly mycotoxin-producing species that could lead to mycotoxin contamination. The occurrence of A. chevalieri and A. amstelodami on peanuts might also reduce shelf life and affect the quality of the kernels. To our knowledge, this is the first report of the occurrence of A. chevalieri and A. amstelodami on a food product in Malaysia, and the finding of this study contributes to the repertoire of Aspergillus species that are associated with food products.
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