The Effect of Roots on the Activity of Soil-borne Plant Pathogens

Mitchell, John E.

doi:10.1007/978-3-642-66279-9_5

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Stimulation of growth by Rhizoctonia solani with the formation of infection cushions as a response to root exudates was reported by many authors (KERR 1956, FLENTJE et al 1963, WYLUE 1959, DODMAN and FLENTJE 1970), In 1968 a correlation between the type of infection cushions formed by R. solani and the mode of fungal penetration into host tissues. They introduced evidence that induction of dome-shaped infection cushions was followed by a direct penetration with or without penetration pegs, while formation of lobate appressoria preceeds penetration through stomata.According to MITCHELL (1976), investigations in this area were unable to confirm a correlation between susceptibility to infection and a selective stimulation by exudates of susceptible tissues.This investigation was carried out to confirm a correlation between susceptibility or resistance of cotton seedlings to R. solani and the selective formation of different types of infection cushion-like structures as a response to root exudates of susceptible or resistant plant tissues.

Materials and Methods

(A) Inoculations of plantsFour Egyptian cotton cuitivars (Giza 67, Giza 68, Giza 69 and Giza 75) were used as test plants. Seeds were germinated on wet filter paper in dark at 30 °C.

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mentioning

confidence: 99%

“…According to MITCHELL (1976), investigations in this area were unable to confirm a correlation between susceptibility to infection and a selective stimulation by exudates of susceptible tissues.…”

mentioning

confidence: 99%

Selective Induction Infection Cushions by Rhizoctonia solani Relation to Host Responses

El-Samra¹,

El-Faham²,

Kamara³

1981

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Stimulation of growth by Rhizoctonia solani with the formation of infection cushions as a response to root exudates was reported by many authors (KERR 1956, FLENTJE et al 1963, WYLUE 1959, DODMAN and FLENTJE 1970), In 1968 a correlation between the type of infection cushions formed by R. solani and the mode of fungal penetration into host tissues. They introduced evidence that induction of dome-shaped infection cushions was followed by a direct penetration with or without penetration pegs, while formation of lobate appressoria preceeds penetration through stomata.According to MITCHELL (1976), investigations in this area were unable to confirm a correlation between susceptibility to infection and a selective stimulation by exudates of susceptible tissues.This investigation was carried out to confirm a correlation between susceptibility or resistance of cotton seedlings to R. solani and the selective formation of different types of infection cushion-like structures as a response to root exudates of susceptible or resistant plant tissues. Materials and Methods (A) Inoculations of plantsFour Egyptian cotton cuitivars (Giza 67, Giza 68, Giza 69 and Giza 75) were used as test plants. Seeds were germinated on wet filter paper in dark at 30 °C. After 72 h, seedlings U.S.

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“…Stimulants most commonly introduced into the soil environment that alleviate fungistasis are components of seed and root exudates released during seed germination and root development. Since the majority of host-parasite interactions in soil do not occur without the release of such stimuli (Curl and Truelove, 1986;Mitchell, 1976), an understanding of the molecules involved in the activation of quiescent fungal propagules by seed and root exudates is of prime importance in understanding the initiation and control of seed and root infections by soil-borne pathogens.…”

Section: Introductionmentioning

confidence: 99%

Exudate molecules initiating fungal responses to seeds and roots

Nelson

¹

1990

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Plant pathogenic fungi survive in soils in a quiescent state. In order for many root-pathogen interactions to be initiated, dormant propagules must be activated by molecules present in seed and root exudates. Without the release of such stimulatory molecules, the majority of root infections do not occur. Currently, little is known about the specific molecules involved in stimulating propagule germination and initiating root-pathogen interactions. Although certain molecules can be shown to elicit germination responses in vitro, responses of propagules reared on conventional culture media do not always reflect the responses of those formed on plant tissues in soil. Consequently, it is not possible to extend conclusions from laboratory determinations of the role of specific exudate molecules in stimulating fungal propagule germination to soil systems. The interaction of Pythium species with germinating seeds has served as a model system to answer questions about propagule behavior and the role of exudate stimulant molecules in establishing root-fungus interactions. The potential role of both volatile and water-soluble molecules in stimulating propagule germination are discussed.

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