Molecular identification of some fungi associated with soft dates (Phoenix dactylifera L.) in Saudi Arabia

Abstract

The Kingdom of Saudi Arabia is considered one of the major dates producing zones in the world, contributing 13% of the total world production. Most of the dates are delivered to local markets without any treatment thus, may be leading to microbial contamination which may increase the incidence of microbial growth. Some pathogenic fungi associated with soft dates (Phoenix dactylifera Linn.) collected from Almadinah Almunawarah, local markets, was isolated and molecularly identified during summer 2019. Contaminated date samples (Sukkary, Ajwa, Shalabi madinah, Barni and Sogea) were placed on PDA plates and incubated at 26°C for 5 days. Morphological and molecular identification of the resulting fungi were investigated. Molecular identification of fungal isolates was conducted using the internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA). Fungal DNAs were amplified by PCR using ITS1-F (5’-TCCGTAGGTGAACCTGCGG-3’) and ITS4 (5’-TCCTCCGCTTATTGATATGC-3’). The purified PCR products were sequenced and the obtained nucleotide sequences were submitted to GenBank on the NCBI. The results showed that the most dominant isolated fungi were Aspergillus niger (100%) associated with “Sogea”, followed by Aspergillus tubingensis (66%) isolated from “Shalabi Almadinah” (40%), Rhizopus stolonifer (36.3%) associated with “Ajwa”, Talaromyces minioluteus (14.2%) isolated from “Sukkary”, respectively. Soft dates are most likely contaminated due to the artificial rise in moisture content and the related inappropriate storage conditions. In conclusion, the study has declared that Aspergillus spp. considered the most fungal contamination of date fruits. Fungal contamination may have an effect on the public health by their mycotoxins which may lead to severe poisoning, diarrhea, emesis, and death. Most date fruits sold and marketed are neither covered nor protected in any way from environmental contamination. If these dates are consumed without thoroughly washing that may induce imminent mycotic infection. The study recommended that prevention of dates fruit mold spoilage should be avoided by application of hazard analysis, critical control point programs and adherence to hygienic good manufacturing practices.

Keywords: Ajwa, Aspergillus niger, Aspergillus tubingensis, PCR, ITS sequencing, molecular identification.

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