Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel
Over the past decade, there have been accumulating reports from farmers and field extension personnel on the increasing incidence and spread of onion (<i>Allium cepa</i>) bulb basal rot in northern Israel. The disease is caused mainly by <i>Fusarium</i> species. Rotting onion...
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MDPI AG
2020-04-01
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| Series: | Biology |
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| Online Access: | https://www.mdpi.com/2079-7737/9/4/69 |
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| author | Ben Kalman Dekel Abraham Shaul Graph Rafael Perl-Treves Yael Meller Harel Ofir Degani |
| author_facet | Ben Kalman Dekel Abraham Shaul Graph Rafael Perl-Treves Yael Meller Harel Ofir Degani |
| author_sort | Ben Kalman |
| collection | DOAJ |
| description | Over the past decade, there have been accumulating reports from farmers and field extension personnel on the increasing incidence and spread of onion (<i>Allium cepa</i>) bulb basal rot in northern Israel. The disease is caused mainly by <i>Fusarium</i> species. Rotting onion bulbs were sampled from fields in the Golan Heights in northeastern Israel during the summers of 2017 and 2018. Tissue from the sampled onion bulbs was used for the isolation and identification of the infecting fungal species using colony and microscopic morphology characterization. Final confirmation of the pathogens was performed with PCR amplification and sequencing using fungi-specific and <i>Fusarium</i> species-specific primers. Four <i>Fusarium</i> spp. isolates were identified in onion bulbs samples collected from the contaminated field: <i>F. proliferatum</i>, <i>F. oxysporum</i> f. sp. <i>cepae</i>, and two species less familiar as causative agents of this disease, <i>F. acutatum</i> and <i>F. anthophilium</i>. Phylogenetic analysis revealed that these species subdivided into two populations, a northern group isolated from white (Riverside cv.) onion bulbs, and a southern group isolated from red (565/505 cv.) bulbs. Pathogenicity tests conducted with seedlings and bulbs under moist conditions proved that all species could cause the disease symptoms, but with different degrees of virulence. Inoculating seeds with spore suspensions of the four species, <i>in vitro</i>, significantly reduced seedlings’ germination rate, hypocotyl elongation, and fresh biomass. Mature onion bulbs infected with the fungal isolates produced typical rot symptoms 14 days post-inoculation, and the fungus from each infected bulb was re-isolated and identified to satisfy Koch’s postulates. The onion bulb assay also reflected the degree of sensitivity of different onion cultivars to the disease. This work is the first confirmed report of the direct and primary cause of <i>Fusarium</i> onion basal rot disease in northeastern Israel. These findings are a necessary step towards uncovering the mycoflora of the diseased onion plants and developing a preventive program that would reduce the disease damage. |
| first_indexed | 2024-03-10T20:44:13Z |
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| issn | 2079-7737 |
| language | English |
| last_indexed | 2024-03-10T20:44:13Z |
| publishDate | 2020-04-01 |
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| spelling | doaj.art-bc5ec0c8101246cdaeb92e36498b0f452023-11-19T20:27:40ZengMDPI AGBiology2079-77372020-04-01946910.3390/biology9040069Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern IsraelBen Kalman0Dekel Abraham1Shaul Graph2Rafael Perl-Treves3Yael Meller Harel4Ofir Degani5Plant Sciences Department, Migal–Galilee Research Institute, Tarshish 2, Kiryat Shmona 11016, IsraelPlant Sciences Department, Migal–Galilee Research Institute, Tarshish 2, Kiryat Shmona 11016, IsraelPlant Sciences Department, Migal–Galilee Research Institute, Tarshish 2, Kiryat Shmona 11016, IsraelThe Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 52900, IsraelDivision for Plant Pests and Diseases, Plant Protection and Inspection Services, Ministry of Agriculture and Rural Development, Bet Dagan 50200, IsraelPlant Sciences Department, Migal–Galilee Research Institute, Tarshish 2, Kiryat Shmona 11016, IsraelOver the past decade, there have been accumulating reports from farmers and field extension personnel on the increasing incidence and spread of onion (<i>Allium cepa</i>) bulb basal rot in northern Israel. The disease is caused mainly by <i>Fusarium</i> species. Rotting onion bulbs were sampled from fields in the Golan Heights in northeastern Israel during the summers of 2017 and 2018. Tissue from the sampled onion bulbs was used for the isolation and identification of the infecting fungal species using colony and microscopic morphology characterization. Final confirmation of the pathogens was performed with PCR amplification and sequencing using fungi-specific and <i>Fusarium</i> species-specific primers. Four <i>Fusarium</i> spp. isolates were identified in onion bulbs samples collected from the contaminated field: <i>F. proliferatum</i>, <i>F. oxysporum</i> f. sp. <i>cepae</i>, and two species less familiar as causative agents of this disease, <i>F. acutatum</i> and <i>F. anthophilium</i>. Phylogenetic analysis revealed that these species subdivided into two populations, a northern group isolated from white (Riverside cv.) onion bulbs, and a southern group isolated from red (565/505 cv.) bulbs. Pathogenicity tests conducted with seedlings and bulbs under moist conditions proved that all species could cause the disease symptoms, but with different degrees of virulence. Inoculating seeds with spore suspensions of the four species, <i>in vitro</i>, significantly reduced seedlings’ germination rate, hypocotyl elongation, and fresh biomass. Mature onion bulbs infected with the fungal isolates produced typical rot symptoms 14 days post-inoculation, and the fungus from each infected bulb was re-isolated and identified to satisfy Koch’s postulates. The onion bulb assay also reflected the degree of sensitivity of different onion cultivars to the disease. This work is the first confirmed report of the direct and primary cause of <i>Fusarium</i> onion basal rot disease in northeastern Israel. These findings are a necessary step towards uncovering the mycoflora of the diseased onion plants and developing a preventive program that would reduce the disease damage.https://www.mdpi.com/2079-7737/9/4/69fungus<i>Fusarium acutatum</i><i>Fusarium anthophilium</i><i>Fusarium oxysporum</i> f. sp. <i>cepae</i><i>Fusarium proliferatum</i>molecular identification |
| spellingShingle | Ben Kalman Dekel Abraham Shaul Graph Rafael Perl-Treves Yael Meller Harel Ofir Degani Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel Biology fungus <i>Fusarium acutatum</i> <i>Fusarium anthophilium</i> <i>Fusarium oxysporum</i> f. sp. <i>cepae</i> <i>Fusarium proliferatum</i> molecular identification |
| title | Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel |
| title_full | Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel |
| title_fullStr | Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel |
| title_full_unstemmed | Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel |
| title_short | Isolation and Identification of <i>Fusarium</i> spp., the Causal Agents of Onion (<i>Allium cepa</i>) Basal Rot in Northeastern Israel |
| title_sort | isolation and identification of i fusarium i spp the causal agents of onion i allium cepa i basal rot in northeastern israel |
| topic | fungus <i>Fusarium acutatum</i> <i>Fusarium anthophilium</i> <i>Fusarium oxysporum</i> f. sp. <i>cepae</i> <i>Fusarium proliferatum</i> molecular identification |
| url | https://www.mdpi.com/2079-7737/9/4/69 |
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