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

Abstract

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.

Characterization of Bioactivity and Antimicrobial Metabolite Production in Bacteria Antagonistic to Plant and Foodborne Molds

“…It is most commonly known for its devastating impact on carrot roots. Among other species, P. sulcatum infect host plants like carrots and cause cavity spot symptoms (El-Tarabily et al 2004). This oomycete uses cell wall degrading enzymes in order to penetrate and colonize the host plant (El-Tarabily et al 2004).…”

“…Among other species, P. sulcatum infect host plants like carrots and cause cavity spot symptoms (El-Tarabily et al 2004). This oomycete uses cell wall degrading enzymes in order to penetrate and colonize the host plant (El-Tarabily et al 2004). This leads to cell wall damage and maceration of tissues, ultimately leading to a product loss due to plant death.…”