The incidence of Alternaria radicina on carrot seeds, seedlings and roots in South Australia

Coles, R.; Wicks, Trevor

doi:10.1071/ap02069

Cited by 17 publications

(11 citation statements)

References 8 publications

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“…Foliar symptoms of A. radicina (causing black rot) (Farrar et al , 2004) are characterised by dark brown to black necrotic lesions, which may be surrounded by a chlorotic halo. Conidia deposited on leaf surfaces will germinate and produce germ tubes, which penetrate the host cell directly to establish an infection site (Coles & Wicks, 2003; Farrar et al , 2004). B. cinerea infects senescent plant tissue and can also enter through wounds.…”

Section: Introductionmentioning

confidence: 99%

Enhanced resistance to foliar fungal pathogens in carrot by application of elicitors

Jayaraman

Rahman

Wan

et al. 2009

Annals of Applied Biology

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Treatment of greenhouse-grown carrot plants with salicylic acid (SA) (100 lM), chitosan (0.02%) and the nutrient-chelate product Alexin (1%) followed 10 h later by inoculation with the necrotrophic fungal pathogens Alternaria radicina and Botrytis cinerea significantly reduced disease development 10 days after inoculation (d.a.i.) compared with control plants sprayed with water. The most effective treatment was chitosan, followed by Alexin and SA. Additional sprays of elicitors resulted in significantly lower disease development 25 d.a.i. Treated plants had elevated transcript levels of pathogenesis-related protein 1 (PR1), chitinase, lipid transfer protein (LTP), chalcone synthase, nonexpressor of PR1 and pathogenesis-related protein 5 (PR5) genes compared with control plants when assayed 10-70 h after treatment. The activity of peroxidase, polyphenoloxidase, phenylalanine ammonia-lyase, chitinase, b-1,3-glucanase and lipoxygenase was significantly increased in elicitor-treated plants compared with control plants 12-72 h after treatment. Microscopic examination of treated leaves revealed reduced fungal growth and colonisation, 48 h after treatment, accompanied by fewer lesions at 120 h, compared with the control. Protein extracts from elicitor-treated plants reduced spore germination and germ tube elongation of the pathogens in vitro by 30-45%. Elicitor-treated plants accumulated higher amounts of total phenolics, 6-methoxymellin and H 2 O 2 compared with the control. Both chitosan and Alexin induced responses similar to that of SA, suggesting that these elicitors may activate the salicylate pathway, leading to induction of defence genes, enzymes, phytoalexin and phenolics, which collectively reduced fungal colonisation.

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Section: Introductionmentioning

confidence: 99%

Enhanced resistance to foliar fungal pathogens in carrot by application of elicitors

Jayaraman

Rahman

Wan

et al. 2009

Annals of Applied Biology

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“…Seed pretreatment with hot water reduced the infected plants rate of 33.0% on savoury essential oil treatment, 22.7% on thyme essential oil treatment, 14.7% on strain FC7B treatment, 26.6% on strain FC8B treatment, 20.7% on strain FC9B treatment and 27.8% on the strain mix. No treatment showed a 100% pathogen control on inoculated seeds; indeed, it is known that seeds treated with fungicides can strongly reduce but not eliminate A. radicina contamination (Coles and Wicks ).…”

Section: Resultsmentioning

confidence: 99%

In vivo Evaluation of Essential Oils and Biocontrol Agents Combined with Hot Water Treatments on Carrot Seeds Against Alternaria radicina

Lopez-Reyes

Gilardi

Garibaldi

et al. 2015

Journal of Phytopathology

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Seed-dressing with essential oils from aromatic plants (savoury and thyme) and with antagonistic bacteria strains (Pseudomonas spp.) was tested after a hot water treatment against Alternaria radicina inoculated on carrot seeds. Seed treatments by immersion in water at 55°C for 10 min improved the efficacy on pathogen control of the treatments with biocontrol agent strains more than the efficacy of those with essential oils. Pretreatment with hot water also increased the germination rate of carrot seeds. A mild phytotoxic effect was observed on the germination rate and the fresh biomass obtained from seeds treated with both essential oils. Treatments with essential oils and antagonistic bacteria presented positive results when combined with hot water dipping of seeds on control of A. radicina, but the effect was not completely additive. The formulation and the application method of the non-chemical products tested are critical on their development as an alternative strategy on seed disinfection.

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“…Other species such as Pythium graminicola and Pythium arrhenomanes are restricted only to Poaceae family (Schroeder et al 2012). Traditional baiting or other culture-based techniques are still widely used for the identification of Pythium species although cultureindependent methods, such as cytochrome oxidase subunit 1 pyrosequencing, are also used (Coffua et al 2016). The challenge is that methodological biases inherent to culture-independent methods may often lead to inconsistencies in diversity estimates of Pythium species associated with dampingoff diseases.…”

Section: ) Parasitismmentioning

confidence: 99%

“…Nevertheless, culture-based techniques are the only means to demonstrate, for example, the presence of potential pathogens even in fields with no previous history of damping-off diseases. Indeed, based on culture-based techniques, several studies have isolated Pythium species from symptomatic and asymptomatic plants and demonstrated their pathogenicity on a large number of plant species (Bahramisharif et al 2013b;Coffua et al 2016). Further, culture-based methods and morphological observations may still result essential in confirming the presence of novel or unexpected species within a sampling location and thus have to be considered for identification purposes (Zitnick-Anderson and Nelson 2014).…”

Section: ) Parasitismmentioning

confidence: 99%

Integrated management of damping-off diseases. A review

Lamichhane

Dürr

Schwanck³

et al. 2017

Agron. Sustain. Dev.

215

133

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Damping-off is a disease that leads to the decay of germinating seeds and young seedlings, which represents for farmers one of the most important yield constraints both in nurseries and fields. As for other biotic stresses, conventional fungicides are widely used to manage this disease, with two major consequences. On the one hand, fungicide overuse threatens the human health and causes ecological concerns. On the other hand, this practice has led to the emergence of pesticide-resistant microorganisms in the environment. Thus, there are increasing concerns to develop sustainable and durable damping-off management strategies that are less reliant on conventional pesticides. Achieving such a goal requires a better knowledge of pathogen biology and disease epidemiology in order to facilitate the decision-making process. It also demands using all available non-chemical tools that can be adapted to regional and specific production situations. However, this still is not the case and major knowledge gaps must be filled. Here, we review up to 300 articles of the damping-off literature in order to highlight major knowledge gaps and identify future research priorities. The major findings are (i) damping-off is an emerging disease worldwide, which affects all agricultural and forestry crops, both in nurseries and fields; (ii) over a dozen of soil-borne fungi and fungus-like organisms are a cause of damping-off but only a few of them are frequently associated with the disease; (iii) damping-off may affect from 5 to 80% of the seedlings, thereby inducing heavy economic consequences for farmers; (iv) a lot of research efforts have been made in recent years to develop biocontrol solutions for damping-off and there are interesting future perspectives; and (v) damping-off management requires an integrated pest management (IPM) approach combining both preventive and curative tactics and strategies. Given the complex nature of damping-off and the numerous factors involved in its occurrence, we recommend further research on critical niches of complexity, such as seeds, seedbed, associated microbes and their interfaces, using novel and robust experimental and modeling approaches based on five research priorities described in this paper.

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The incidence of Alternaria radicina on carrot seeds, seedlings and roots in South Australia

Cited by 17 publications

References 8 publications

Enhanced resistance to foliar fungal pathogens in carrot by application of elicitors

Enhanced resistance to foliar fungal pathogens in carrot by application of elicitors

In vivo Evaluation of Essential Oils and Biocontrol Agents Combined with Hot Water Treatments on Carrot Seeds Against Alternaria radicina

Integrated management of damping-off diseases. A review

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