Influence of Fusarium spp. isolate and inoculum density on resistance screening tests in onion

Caligiore-Gei, Pablo F.; Valdez, J. G.; Piccolo, R. J.; Galmarini, Claudio R.

doi:10.1590/s1982-56762014005000005

Cited by 24 publications

(25 citation statements)

References 13 publications

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“…F. proliferatum can survive for extended periods in soil, so it is best to avoid planting the same field repeatedly with either onion or garlic [9]. F. proliferatum was reported in onion in different countries, including the United States [10], Serbia [6], Argentina [11], The Netherlands, Uruguay [12], Sweden [13], and Germany [14].…”

Section: Introductionmentioning

confidence: 99%

Isolation and Identification of Fusarium spp., the Causal Agents of Onion (Allium cepa) Basal Rot in Northeastern Israel

Kálmán

Abraham

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et al. 2020

Biology

111

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Over the past decade, there have been accumulating reports from farmers and field extension personnel on the increasing incidence and spread of onion (Allium cepa) bulb basal rot in northern Israel. The disease is caused mainly by Fusarium 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 Fusarium species-specific primers. Four Fusarium spp. isolates were identified in onion bulbs samples collected from the contaminated field: F. proliferatum, F. oxysporum f. sp. cepae, and two species less familiar as causative agents of this disease, F. acutatum and F. anthophilium. 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, in vitro, 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 Fusarium 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.

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Section: Introductionmentioning

confidence: 99%

Isolation and Identification of Fusarium spp., the Causal Agents of Onion (Allium cepa) Basal Rot in Northeastern Israel

Kálmán

Abraham

Graph

et al. 2020

Biology

111

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“…The most widely practiced Horticulturae 2020, 6, 26 2 of 14 method to develop FBR-resistant onion cultivars is a seedling screening in a controlled environment, such as a greenhouse or growth chamber. Using these conditions, FBR-resistant seedlings are selected either by artificially inoculating sterile onion seeds [10,11] or the growing media [12][13][14][15] with one [16], two [10], three [12,15], or multiple [13,14] virulent FOC isolates. Also, evaluation of mature bulbs for FBR resistance can be done using field inoculation that use natural FOC infestation [10] or artificial inoculation of a field plot [11].…”

Section: Introductionmentioning

confidence: 99%

“…In addition to genetic background and aging, environmental factors could also change R-gene transcript levels and in turn disease resistance [20,22]. During an onion seedling screening, environmental variability and plant aging could be avoided when completed inside a growth chamber or greenhouse for a short period of time [13,14]. Nonetheless, in field screening, an optimum screening would not be possible due to a non-uniform field distribution of multiple pathogen isolates [23] in variable soil and nutritional conditions, which could influence susceptibility reaction to FOC [24].…”

Section: Introductionmentioning

confidence: 99%

Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection

et al. 2020

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The development of Fusarium Basal Rot (FBR)-resistant onion cultivars through field and seedling screening approaches faces tremendous challenges due to non-uniform distribution of the disease pathogen and possible multiple mechanisms of host–plant resistance. This study compared the efficiencies of these two methods for increasing FBR resistance of short-day onion after a single selection cycle. Asymptomatic plants or bulbs of seven onion cultivars were selected using a seedling screen performed in a growth chamber or a field screening of mature bulbs. Original and selected populations were evaluated for their responses to FBR stress thereafter employing the same two methods used for screening. The field screening of mature bulbs was found unreliable in both selection and evaluation, likely due to a non-random distribution of the FBR pathogen and variable environmental factors present in the field. The seedling screening successfully increased FBR resistance in the selected cultivar populations revealed by a seedling evaluation. From the results, it is recommended to use a consistent method for both screening and evaluation to make the most selection progress.

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“…Many reports mention several resistant cultivars in different parts of the world (Cramer 2000;Gutierrez et al 2006;Taylor et al 2013), but some of them, when tested in the Argentinian conditions, reacted as susceptible. One of the hypothesis is the occurrence of more disease-conducive conditions for the field, especially in the presence of more aggressive inoculum (Caligiore-Gei et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…This has been achieved through recurrent selection of best-forming individuals in field conditions (Galmarini et al 2003). Alternatively, controlled environment assays have been developed to evaluate FBR resistance of onion accessions and varieties (Caligiore-Gei et al 2014). In those, it is not uncommon to observe individuals remaining healthy for longer compared to others (Galván et al 2008), which can be due to methodological issues (escape mechanism) or active resistance mechanisms triggered in the surviving individuals.…”

Section: Introductionmentioning

confidence: 99%

Breeding onion for resistance to Fusarium basal rot: comparison of field selection and artificial inoculation

Caligiore-Gei

Ciotti

Valdez

et al. 2020

Trop. plant pathol.

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Fusarium basal rot (FBR) is one of the main onion diseases in Argentina. The Onion Breeding National Program, held at INTA Experimental Station in La Consulta, Argentina, has developed onion breeding lines with increased resistance to FBR through a selection scheme performed under field conditions. The aim of the present work was to evaluate the achieved response to selection in the FBR resistance trait, comparing two strategies: selection under field environment and artificial inoculations performed in controlled conditions. Seeds of the breeding line 17-1289 (P 0) were inoculated with Fusarium oxysporum f.sp. cepae (isolate FOC LJC10081), one seed per cap. After 15 days 162 surviving plants were treated with fungicide and transplanted. The resulting bulbs were planted and recombined avoiding contamination with foreign pollinators. The obtained seeds were labelled as PCC (Progeny generated under Controlled Conditions). Another portion of P 0 seeds was grown under field conditions in a FBR-conductive soil. The best bulbs were selected at harvest based on their FBR resistance score, root system quality and agronomic features. These bulbs later produced seeds by recombination in isolation and were labelled as PFC (Progeny generated under Field Conditions). The P 0 population and the PCC-PFC progenies were then compared through a standardized test for determination of FBR resistance, using two inoculum concentrations in the substrate. The incidence of FBR was significantly reduced in PCC at high inoculum concentrations, in comparison to the original population P 0. Disease progression was delayed and lower rates were achieved in PCC. The described lab selection technique may constitute an interesting and useful tool to select materials that carry genetic resistance and contribute to an integrative approach, complemented with selection under field conditions, in onion breeding programs for FBR resistance.

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Influence of Fusarium spp. isolate and inoculum density on resistance screening tests in onion

Cited by 24 publications

References 13 publications

Isolation and Identification of Fusarium spp., the Causal Agents of Onion (Allium cepa) Basal Rot in Northeastern Israel

Isolation and Identification of Fusarium spp., the Causal Agents of Onion (Allium cepa) Basal Rot in Northeastern Israel

Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection

Breeding onion for resistance to Fusarium basal rot: comparison of field selection and artificial inoculation

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