Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia

El‐Tarabily, Khaled A.; Hardy, G.E.St.J.; Sivasithamparam, Krishnapillai

doi:10.1046/j.1365-3059.1996.d01-8.x

Cited by 22 publications

(14 citation statements)

References 25 publications

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“…Definitive evidence for the biological origin of this soil-borne disease was provided by Groom and Perry (1985) and then by White (1988), who established that two slow-growing Pythium species, P. violae (Chesters and Hickman) and P. sulcatum (Pratt and Mitchell), were the most important causal organisms in countries where cavity spot occurred. Several fast-growing Pythium species including P. ultimum (Trow) (Vivoda et al 1991) and P. coloratum (Vaartaja) (El-Tarabily et al 1996) have also been demonstrated to cause cavity spot.…”

Section: Mots Clésmentioning

confidence: 99%

“…Within 24 h of sampling, the carrots were cleaned under running water for 4 h to remove soil particles and surface microorganisms (El-Tarabily et al 1996). Two hundred pieces (ca.…”

Section: Isolation Of Pythium Spp Associated With Cavity Spot Lesionsmentioning

confidence: 99%

“…The pieces were surface-disinfested by immersion in 70% ethyl alcohol for 3 min followed by immersion in 1.05 % sodium hypochlorite for 4 min. Surface-disinfested pieces were then rinsed 10 times (5 min for each rinse) with sterile, distilled water to remove residual hypochlorite, and then dried on sterile filter paper for 30 min in a laminar flow cabinet (El-Tarabily et al 1996). Tissues from the lesion margins were then excised aseptically and plated with the internal tissue facing down, on a modified selective medium (Jeffers and Martin 1986) for the isolation of Pythium species.…”

Section: Isolation Of Pythium Spp Associated With Cavity Spot Lesionsmentioning

confidence: 99%

“…Inoculum for each Pythium isolate was prepared by placing 40 g of moist millet seed (Panicum miliaceum L.) into 250-mL Erlenmeyer flasks and autoclaving at 121°C for 30 min on 3 consecutive days (El-Tarabily et al 1996). The substrate was then aseptically inoculated with eight agar plugs (5-mm diameter) taken from the actively growing margins of the selected Pythium isolates grown on PCA.…”

Section: Glasshouse Pathogenicity Test Inoculum Productionmentioning

confidence: 99%

“…Each isolate was dispersed through the soil using 0.05 g millet seed inoculum g -1 air-dried soil by mixing in a cement mixer. This inoculum density had previously been shown to be the optimum level required to cause cavity spot under glasshouse conditions (El-Tarabily et al 1996). Colonized millet seeds were autoclaved and used as the control.…”

Section: Soil Infestationmentioning

confidence: 99%

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Pythium sulcatum and P. ultimum as causal agents of cavity spot disease of carrots in Egypt

El‐Tarabily¹,

Abouzeid²,

Hardy³

et al. 2004

Can. J. Plant Sci.

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El-Tarabily, K. A., Abouzeid, M. A., Hardy, G. E. ST. J. and Sivasithamparam, K. 2004. Pythium sulcatum and P. ultimum as causal agents of cavity spot disease of carrots in Egypt. Can. J. Plant Sci. 84: 607-614. In a survey of carrot diseases of the Nile delta region of northern Egypt, Pythium sulcatum (Pratt and Mitchell) and P. ultimum (Trow) were isolated from 74 and 26%, respectively, of carrot roots showing cavity spot disease. In laboratory and glasshouse pathogenicity tests, P. sulcatum caused significantly (P < 0.05) more severe damage than P. ultimum. The greater level of pathogenicity of P. sulcatum was associated with its ability to produce a wider array of cell-wall-degrading enzymes with significantly (P < 0.05) higher enzymatic activities compared to P. ultimum. Polygalacturonase, pectin lyase, pectate lyase and cellulase were detected in cavity spot lesions induced by both P. sulcatum and P. ultimum. Pectin methylesterase was detected in tissues invaded by P. sulcatum and not by P. ultimum. This is the first record of cavity spot disease of carrots in Egypt and indicates P. sulcatum and P. ultimum as the causal agents of this disease in the region surveyed.Key words: Carrots, cavity spot, cell-wall-degrading enzymes, Egypt, Pythium El-Tarabily, K. A., Abouzeid, M. A., Hardy, G. E. ST. J. et Sivasithamparam, K. 2004. La cavité pythienne de la carotte causée par Pythium sulcatum et P. ultimum en Égypte. Can. J. Plant. Sci. 84: 607-614. Dans le cadre d'une enquête sur les maladies de la carotte dans la région du delta du Nil, dans le nord de l'Égypte, on a isolé Pythium sulcatum (Pratt et Mitchell) et P. ultimum (Trow) dans 74 % et 26 % des carottes atteintes de la cavité pythienne, respectivement. Lors des essais de pathogénicité en laboratoire et en serre, P. sulcatum a entraîné des dommages significativement (P< 0,05) plus importants que P. ulitimum. On associe la plus grande pathogénicite de P. Sulcatum au fait que le cryptogame produit un plus large éventail d'enzymes détruisant la paroi cellulosique et que l'activité de ces enzymes est significativement plus élevée (P < 0,05) que chez P. ultimum. On a retrouvé de la polygalacturonase, de la pectine lyase, de la pectate lyase et de la cellulase des deux pathogènes dans les lésions caverneuses. Les tissus envahis par P sulcatum contenaient aussi de la pectine méthylestérase, mais pas ceux attaqéus par P. ulitimum. Il s'agit de la première fois où l'on observe la cavité pythienne en Égypte et tout indique que cette maladie résulte de P. sulcatum et P. ultimum dans la région atteinte.

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Section: Mots Clésmentioning

confidence: 99%

“…Within 24 h of sampling, the carrots were cleaned under running water for 4 h to remove soil particles and surface microorganisms (El-Tarabily et al 1996). Two hundred pieces (ca.…”

Section: Isolation Of Pythium Spp Associated With Cavity Spot Lesionsmentioning

confidence: 99%

Section: Isolation Of Pythium Spp Associated With Cavity Spot Lesionsmentioning

confidence: 99%

Section: Glasshouse Pathogenicity Test Inoculum Productionmentioning

confidence: 99%

Section: Soil Infestationmentioning

confidence: 99%

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Pythium sulcatum and P. ultimum as causal agents of cavity spot disease of carrots in Egypt

El‐Tarabily¹,

Abouzeid²,

Hardy³

et al. 2004

Can. J. Plant Sci.

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Evaluation of fungicides for the control of carrot cavity spot

Martinez

Lévesque

Bélanger

et al. 2005

Pest Management Science

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Cavity spot is one of the most common and serious diseases of carrot (Daucus carota L). The disease, caused by different species of Pythium, including P. violae Chesters & Hickman, P. sulcatum Pratt & Mitchell and P. sylvaticum Campbell & Hendrix, leads to frequent high rejection rates during grading worldwide. In the area of the city of Québec, the disease is caused mainly by P. sulcatum, P. sylvaticum and P. macrosporum Vaartaja & van der Plaats-Niterink. Cavity spot can be controlled with metalaxyl, but reports are emerging that this treatment show little or no efficacy in many regions. This situation reinforces the need for alternative fungicides. The objectives of the present study were: (1) to determine the sensitivity of 14 pathogenic isolates of P. sulcatum, P. sylvaticum and P. macrosporum collected from carrots produced in the area of the city of Québec to different broad-spectrum and oomycete-specific fungicides (chlorothalonil, etridiazole, fludioxonil, fosetyl-Al, metalaxyl, zoxamide), (2) to evaluate the efficacy of the fungicides in controlling cavity spot, and (3) to evaluate the risk of resistance development of isolates with the best-performing fungicide(s). The determination of EC50 for the fungicides tested showed that most isolates were highly sensitive to both metalaxyl and zoxamide but insensitive to fludioxonil, fosetyl-Al and chlorothalonil. In greenhouse assays, only zoxamide provided significant and consistent disease control as measured by the number of cavity spot lesions caused by P. sulcatum. Investigations into the risk of resistance development to zoxamide showed that, for specific isolates, repeated exposure to the fungicide resulted in a loss of sensitivity.

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Diseases of Carrot

Higgins¹,

Hausbeck²

2023

Handbook of Plant Disease Management

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**Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia**

Cited by 22 publications

References 25 publications

Pythium sulcatum and P. ultimum as causal agents of cavity spot disease of carrots in Egypt

Pythium sulcatum and P. ultimum as causal agents of cavity spot disease of carrots in Egypt

Evaluation of fungicides for the control of carrot cavity spot

Diseases of Carrot

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