Clarification of the agents causing blue mold storage rot upon various flower and vegetable bulbs: implications for mycotoxin contamination (original) (raw)
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Canadian Journal of Botany, 2005
Fifteen strains representing each Penicillium ser. Corymbifera taxa were compared using phenotypic and chemotaxonomic characters by cluster analysis and discriminant partial least squares regression. Variability in phenotypic expression of species strains resulted in a more fragmented classification compared with secondary metabolite expression. Although the observed phenotypic expression varied for strains cultured upon the same media, it was possible to classify strains into species groupings based only upon a few distinctive phenotypic traits. Data analysis of secondary metabolite profiles generated from HPLC-diode array dectection analysis gave reliable strain classification when more than one media type was employed. Depending on the species, Czapek yeast autolysate agar typically yielded the greatest chemical diversity; however, several metabolites (terrestric acid, corymbiferone, the corymbiferan lactones, and daldinin D) were only produced when strains were grown on either y...
Fungi Associated with Storage Rots of Onion Bulbs in Sokoto. Nigeria
International Journal of Modern Botany, 2012
A survey of fungi associated with postharvest deterioration of onion bulbs was conducted in Sokoto, northwestern Nigeria in 2010. Rotten onion bulbs sold at five different markets: Sokoto central markets, Kasuwa daji, Gawon nama, Arkilla and Mabera were infected with eight species of fungi: Aspergillus niger, A. flavus, A. fumigatus, Alternaria porri, Rhizopus stolonifer, Fusarium oxysporum, and Penicillium citrinum. Of these, A.niger, A.flavus and A.porri were the most frequently isolated fungi. Penicillium citrinum was the least encountered fungus. Pathogenicity tests revealed that all the isolated fungi were pathogenic on onion bulbs however; A. porri, R. stolonifer and P. citrinum were the most pathogenic leading to rapid disintegration of the infected bulbs within 21 days of inoculation. While A. niger was the least pathogenic. The implications of the findings in relation to post harvest handling of onion bulbs and mycotoxin production were discussed.
New Penicillium Species Associated with Bulbs and Root Vegetables
Systematic and Applied Microbiology, 2003
Taxa of the Penicillium series Corymbifera are known for their strongly fasciculate growth and association with the rhizosphere of vegetables and flower bulbs. Using micromorphology, colony characteristics on various media and chemotaxonomic profiling, P. albocoremium sensu stricto and two new species, P. radicicola and P. tulipae, are redescribed during a taxonomic survey of P. albocoremium isolates contained within the IBT culture collection. Although these novel taxa are micromorphologically quite similar, their unique secondary metabolite profiles individually distinguish them from isolates of P. albocoremium. Moreover, the following metabolites produced by these species are known mycotoxins: citrinin, penicillic acid and terrestric acid by P. radicicola and terrestric acid and penitrem A by P. tulipae. tion [18] and volatile metabolite production [7] demonstrated several discrepancies indicating that P. albocoremium sensu lato may contain two or more taxa.
Bulb and root rot in lily (Lilium longiflorum) and onion (Allium cepa) in Israel
In the past 10 years, there has been a substantial increase in reports, from growers and extension personnel, on bulb and root rots in lily (Lilium longiflorum) in Israel. Rot in these plants, when grown as cut flowers, caused serious economic damage expressed in reduction in yield and quality. In lily, the fungal pathogens involved in the rot were characterized as binucleate Rhizoctonia AG-A, Rhizoctonia solani, Pythium oligandrum, Fusarium proliferatum (white and purple isolates) and F. oxysporum, using morphological and molecular criteria. These fungi were the prevalent pathogens in diseased plants collected from commercial greenhouses. Pathogenicity trials were conducted on lily bulbs and onion seedlings under controlled conditions in a greenhouse to complete Koch's postulates. Disease symptoms on lily were most severe in treatments inoculated with binucleate Rhizoctonia AG-A, P. oligandrum and F. proliferatum. Plant height was lower in the above treatments compared with the control plants. The least aggressive fungus was R. solani. In artificial inoculations of onion, seedling survival was significantly affected by all fungi. The most pathogenic fungus was F. proliferatum w and the least were isolates of F. oxysporum (II and III). All fungi were successfully re-isolated from the inoculated plants.
Storability of Onion Bulbs Contaminated by Aspergillus niger Mold
In the course of pre-and postharvest epidemiological studies on bulbs contamination by Aspergillus niger, two Sudanese onion cultivars were tested: 'Saggai Red' and 'EI-Hilo White'. A. niger spores, whether seedbome, soilborne or airborne, were avirulent to the healthy growing onion plants. The fungus heavily contaminated the dead onion tissues, mainly the dead leaves followed by the dry scales, the dead roots and, to a lesser extent, the bulb necks, preferring the red-skinned cultivar to the white one. The initial spores carried from naturally contaminated field soil on the dead tissues could germinate and produce massive numbers of new spores on bulbs stored at average climatic conditions of Sudan (23-39~ 29-93% relative humidity). Under laboratory-controlled conditions, optimal growth occurred at 75-85% r.h. on bulbs with dry scales and maximum losses occurred at 100% r.h. and ambient temperature. Under in vitro conditions, the optimal growth and sporulation temperature for A. niger was in the range of 30-35~ Early harvesting and removal of the dead onion tissues improved bulb storability in aseptic stores under low temperature and relative humidity conditions.
International Journal of Pathogen Research, 2020
Onion (Allium cepa L.) is a highly nutritive vegetable with about 2 million metric tons grown annually in Nigeria, but the majority is lost to postharvest spoilage, especially through microbial infection. In this study, we identified bacteria and fungi associated with postharvest spoilage in onion bulbs and determined the pathogenicity of the bacterial isolates. Two weeks stored onion bulbs were purchased at a market in Ile-Ife, rinsed in 5% HOCL and aseptically cut into seven sections each. The fourteen sections obtained were swabbed daily with sterile cotton-tipped applicators for seven days. The swabs were streaked onto the surface of Nutrient Agar (NA) and selective/differential media plates for the isolation of bacteria, and Potato Dextrose Agar (PDA) plates for the cultivation of fungi. The bacterial plates were incubated at 37°C for 24 hours, while the fungal plates were incubated at 25°C for 5 days. The isolates were identified based on standard microbiological methods. Pathogenicity tests of the bacterial isolates from each of the genera was carried out by re-inoculation on the inner tissues of fresh onion bulbs that have been cleaned with 1% NaOCL, an uninoculated onion bulb served as the control. Thirty-five (35) bacterial isolates belonging to four different genera were identified, which included; 11 (31.4%) Staphylococcus spp., 9 (25.7%) Micrococcus spp., 8 (22.9%) Bacillus spp. and 7 (20%) Original Research Article Torimiro et al.; IJPR, 5(2): 39-45, 2020; Article no.IJPR.61173 40 Flavobacterium spp. Seven (7) fungal isolates were identified which included; 5 (71.4%) Aspergillus fumigatus, 1 (14.3%) Gibellula suffulta and 1 (14.3%) Hirsutella saussueri. Pathogenicity tests revealed that all the bacterial isolates were able to cause rot in onion in comparison with the control which had no observable rot; Flavobacterium spp. (28 mm) was the most pathogenic, while Micrococcus spp. was the least pathogenic (14 mm) based on the diameter of rot formation within seven days. These findings revealed that spoilage microorganisms can cause onion rot, hence, onions already showing contamination symptoms should be separated from fresh ones to avoid cross-contamination, while adequate care should be taken before consumption of onion to avoid foodborne illnesses and diseases.
Onion bulbs rots are caused by microorganisms especially fungi leading to economic loss. These fungi have been known to produce toxins which are injurious to human and animal health, therefore in this study, the fungi associated with the spoilage of onions bulbs purchased from Umuike, Amaikwo, Amaudo, Okpuno and Permanent site markets were isolated, characterized and identified. The average fungal counts ranged between 1.2 x 103 CfU/ml and 2.0 x 103 CfU/ml. The fungi isolated from the spoilt onion bulbs were Penicillum digitatum, Fusarium oxysporum, Rhizopus stolonifer, Alternaria alternata, Aspergillus niger and Saccharomyces cerevisiae. The samples from Amaudo market had the highest percentage distribution of fungi of 34.2% while those from permanent site had the least percentage distribution of 8.6%. Aspergillus niger had the highest percentage distribution of 34.29% in the spoilt onion bulbs while Saccharomyces cerevisiae had the least percentage distribution of 5.71%. Aspergillus niger also had the highest rot diameter of 40mm while Saccharomyces cerevisiae had the least rot diameter of 16mm. Adequate mycological knowledge, storage facilities and handling practices would therefore minimize the deterioration of onion bulbs thereby ensuring its availability to the society all year round.
Evaluation of Onion Cultivars for Resistance to Aspergillus niger, the Causal Agent of Black Mold
Journal of the American Society for Horticultural Science, 2002
Black mold (BM), caused by Aspergillus niger Tiegh., is a common onion (Allium cepa L.) postharvest disease under hot and humid storage conditions. This study aimed to develop a BM screening protocol, to evaluate onion cultivars for resistance. The effects of pathogen isolate, inoculum density, incubation temperature, and inoculation method on severity of BM were investigated in designing the screening protocol. Variation in virulence was observed and two highly virulent subcultures, An4-2 and An39-3, were selected for study. Disease severity, both in lesion size and sporulation degree, increased with higher inoculum densities and incubation temperatures. In contrast, small lesions and no sporulation were observed when onion scales were inoculated with 1 × 10 4 spores/mL or incubated at temperatures lower than 20 °C. Inoculation of onion scales or entire bulbs were compared and scale inoculation correlated better with BM incidence in storage. The procedure for BM screening protocol included: wound inoculation of onion slices with 40 µL inoculum suspension of 1 × 10 5 spores/mL, incubation at 25 °C with 12 hour photoperiod, and rating lesion diameter and sporulation 4 days after inoculation. Using this screening protocol, 42 onion cultivars were evaluated and cultivars with better storability such as 'Red Pinoy', 'Serrana', 'Dehydrator No.3', and 'Moonlight' were tolerant to A. niger. These cultivars showed small lesions and no sporulation during screening. On the other hand, cultivars with poor storability like 'Texas Early Grano 502', 'Granex 429', and 'Explorer' exhibited larger lesions with profuse sporulation. Lesion diameter caused by the scale inoculation correlated significantly with bulb storage loss (r = 0.51, P < 0.01) as well as with bulb dry matter (r =-0.48, P < 0.01) and total soluble solids (r =-0.51, P < 0.01). The screening protocol and tolerant materials are now successfully used in the Asian Vegetable Research and Development Center onion breeding program for resistance to black mold.
Foods, 2021
In recent years, different postharvest alterations have been detected in garlic. In many cases, the symptoms are not well defined, or the etiology is unknown, which further complicates the selection of bulbs during postharvest handling. To characterize the different symptoms of bulb rot caused by fungi, garlic bulb samples were collected from six Spanish provinces in two consecutive years. Eight different fungal species were identified. The most prevalent postharvest disease was Fusarium dry rot (56.1%), which was associated with six Fusarium species. Fusarium proliferatum was detected in more than 85% of symptomatic cloves, followed by F. oxysporum and F. solani. Pathogenicity tests did not show a significant correlation between virulence and mycotoxin production (fumonisins, beauvericin, and moniliformin) or the mycelial growth rate. Penicillium allii was detected in 12.2% of the samples; it was greatly influenced by the harvest season and garlic cultivar, and three different morp...
Control of Soilborne Pathogenic Fungi in Fields of Sweet Onion
Plant Disease, 1997
Populations of soil fungi from fields planted to sweet onion were assayed on selective media. In pathogenicity tests, Rhizoctonia solani AG-4, Pythium irregulare, and Phoma terrestris were the fungi most virulent on onion seedlings. Plots were fumigated with methyl bromide (MBR), chloropicrin (CP), MBR + CP (67% + 33%), metam sodium, 1,3,-dichloropropene (1,3-D), or 1,3-D + 17% CP in four field experiments in 2 years. Sweet onion was transplanted or direct seeded in October or November and harvested in April or May. MBR + CP and CP were effective in reducing populations of Phoma terrestris, Pythium spp., Fusarium spp., and R. solani AG-4 in soil. Metam-sodium and 1,3-D + 17% CP were less efficacious, and MBR and 1,3-D were ineffective. There were no differences in the percentage of bulbs with decay at harvest or after curing among treatments. Increased yield of marketable bulbs was associated with control of soilborne pathogenic fungi. In fields continuously cropped to onion, decrea...