Showing papers on "Phytoalexin published in 1976"

Host-Pathogen Interactions: XII. Response of Suspension-cultured Soybean Cells to the Elicitor Isolated from Phytophthora megasperma var. sojae, a Fungal Pathogen of Soybeans

Abstract: The glucan elicitor isolated from the mycelial walls of Phytophthora megasperma var. sojae, the fungus which causes stem and root rot in soybeans, stimulates the activity of phenylalanine ammonia-lyase and the accumulation of glyceollin in suspension-cultured soybean cells. Nigeran, a commercially available fungal wall glucan, was the only other compound tested which has any activity in this system. Glyceollin is a phenylpropanoid-derived phytoalexin which is toxic to P. megasperma var. sojae. Evidence is presented to support the hypothesis that the action of elicitors in stimulating phytoalexin synthesis is not species or variety specific but, rather, is part of a general defensive response of plants.

Phytoalexin induction as a new dynamic approach to the study of systematic relationships among higher plants

Abstract: IT is well established that many higher plants respond to microbial invasion by the de novo production of organic substances called phytoalexins1,2. These compounds are absent from healthy plants and are induced by the attacking microorganisms. Although the role of phytoalexins in disease resistance is not yet entirely clear, considerable evidence suggests that they are of importance in the protection of higher plants from fungal colonisation. Although few surveys have been attempted, there is clearly a taxonomic element in phytoalexin biosynthesis, in that different plant families accumulate chemically different types of compounds3. Thus, the Leguminosae in general produce isoflavonoids, the Solanaceae diterpenes, the Compositae polyacetylenes and so on2; anomalies are rare, for example, the furanoacetylene, wyerone acid, from Vicia faba (Leguminosae)4. As lesser variations also occur within these families, there is the clear possibility of using phytoalexin induction as a tool in taxonomic studies. We report here the first successful application of this technique to the problems of classification at the generic and species level in the Leguminosae.

The possible rôle of phytoalexins in the resistance of sugarbeet (Beta vulgaris) to Cercospora beticola

Abstract: Leaves of sugarbeet ( Beta vulgaris ) infected with Cercospora beticola yield two compounds, the flavanone betagarin (C 18 H 16 O 6 ) and the isoflavone betavulgarin (C 17 H 12 O 6 ) Highly resistant cultivars appear to produce greater quantities of betavulgarin in the lesions than the more susceptible ones Betavulgarin possesses strong antifungal activity whereas betagarin does not It also has many of the properties of a phytoalexin and could play an important role in the resistance of sugarbeets to Cercospora beticola The significance of betagarin is not so clearly defined Betavulgarin possesses greater antifungal activity than the well-known active isoflavones such as biochanin A, formononetin and genistein

Identification of medicarpin as a phytoalexin in the broad bean plant (Vicia faba L.)

Abstract: THE analysis of phytoalexin induction has been proposed as a dynamic approach to plant systematics1. It has also been pointed out that production of the furanoacetylene wyerone acid2 by Vicia faba is an intriguing anomaly to the more general accumulation of isoflavanoid phytoalexins by members of the Leguminosae. In our studies on phytoalexin production by V. faba, three related furanoacetylenes (Fig. 1), wyerone acid (a), wyerone (b)3 and wyerone expoxide (c)4, have been identified as the major components of the multiple phytoalexin response of the broad bean plant to fungal infection5. In addition to these phytoalexins other minor inhibitors were detected in bioassays of thin layer chromatograms of methanol extracts of infected tissues5. Only one of these inhibitors reacted with p-nitroaniline6 to give an orange coloration indicating phenolic character. No anti-fungal compounds were detected in extracts of healthy tissues. Here we report the identification of the phenolic inhibitor as medicarpin (3-hydroxy-9-methoxy pterocarpan) (Fig. 1d), a phytoalexin present in a wide range of leguminous species1.

Suppression of bacterially-induced hypersensitive reaction and phytoalexin accumulation in bean by phaseotoxin

Abstract: PHASEOTOXIN is a trivial name given to an exotoxin produced by Pseudomonas phaseolicola, which causes halo blight of beans1. Although the mechanism of chlorosis induction in susceptible hosts is unknown, evidence indicates that chlorosis is casually related to inhibition of ornithine carbamoyltransferase (OCT; EC 2.1.3.3) by phaseotoxin, a potent and specific inhibitor of the enzyme2. Phaseotoxin may also be involved in the host specificity of the pathogen. We previously reported that in infected resistant bean plants (but not in infected susceptible ones) phaseotoxin production is suppressed in spite of substantial bacterial multiplication3. Further, in resistant beans treated with phaseotoxin, a larger number of bacteria are found than in non-treated plants4. These observations indicate that phaseotoxin may suppress the hypersensitive reaction (HR) in resistant hosts. The object of this study was to investigate whether pretreatment of resistant cultivars of bean with phaseotoxin suppresses the HR response of the host and phytoalexin accumulation on subsequent inoculation with P. phaseolicola, and our results seem to support this.

Xii. response of suspension-cultured soybean cells to the elicitor isolated from phytophthora megasperma var. sojae, a fungal pathogen of soybeans1

Abstract: The glucan elicitor isolated from the mycelial walls of Phytophthora megasperma var. sojae, the fungus which causes stem and root rot in soybeans, stimulates the activity of phenylalanine ammonia-lyase and the accumulation of glyceollin in suspension-cultured soybean cells. Nigeran, a commercially available fungal wall glucan, was the only other compound tested which has any activity in this system. Glyceollin is a phenylpropanoid-derived phytoalexin which is toxic to P. megasperma var. sojae. Evidence is presented to support the hypothesis that the action of elicitors in stimulating phytoalexin synthesis is not species or variety specific but, rather, is part of a general defensive response of plants.

Notizen: Isosativan: an Isoflavan Phytoalexin from Trifolium hybridum and other Trifolium Species

Abstract: The disease resistance of many higher plants may depend on the post-infectional accumulation of antifungal compounds called phytoalexins1. In general, species of the Leguminosae (subfamily Lotoideae) produce isoflavonoid phytoalexins (pterocarpans and isoflavans) although one exception (the furanoacetylene, wyerone acid from Vicia jaba) has been reported 2. During a phytochemical survey of the genus Trijolium, it was found that in addition to known compounds, the fungus-infected leaves of alsike clover (T . hybridum L.) produced an iso­ flavonoid not previously described as a phytoalexin. From the evidence presented below, this compound has been formulated as vestitol-7-O-methyl ether (1). Phytoalexins were isolated from the detached leaves of T. hybridum using the drop-diffusate tech­ nique as previously described 3. Conidial suspensions of the non-pathogenic fungus, Helminthosporium carbonum Ullstrup served as the phytoalexin in­ ducer. Diffusates from infected leaves were extracted with EtOAc and the organic fractions bulked and reduced to dryness. TLC (CHC13 : MeOH, 100 : 2, Merck, Si-gel F254 , 0.25 mm) of the residue af­ forded three major phenolic zones at Rp 0.14 (Band 1), 0.47 (Band 2) and 0.55 (Band 3 ); a minor zone (Band 4) was also apparent at approx. Rp 0.66. The Band 1 component was purified in /i-pentane : Et20 : HOAc (PEA) (75 : 25 : 3, 3 X ) to afford the known isoflavan phytoalexin, vestitol4