Phytophthora megasperma

Davidse, L.C., Hofman, A.E., Velthuis, G.C.M. 1983. Specific interference of metalaxyl with endogenous RNA polymerase activity in isolated nuclei of Phytophthora megasperma f.sp.medicaginis. Exp. Mycol. 344-361. 

Giannini, J.L., Holt, J.S., Briskin, D.P. The effect of glyceollin on proton leakage in Phytophthora megasperma f.sp. glycinea plasma membrane and red beet tonoplast vesicles. Plant Sci 1990 68 39-45. 

GRAHAM, T.L., KIM, J.E., GRAHAM, M.Y., Role of constitutive isoflavone conjugates on die accumulation of glyceollin in soybeans infected with Phytophthora megasperma Mol. Plant-Microbe Interact., 1990,3,157-166. 

Cell wall preparations of Phytophthora megasperma Glycine max. phenylalanine ammonia lyase chalcone synthase (44)... 

Our own research group reported the first evidence suggesting occurrence of race specific ellcitors In Phytophthora megasperma... 

Table I. Effect of Metalaxyl (0.1 pg/ml) on Incorporation of Labeled Precursors by Mycelium of Phytophthora megasperma f.sp. medicaginis...

The production of fit laboratory-induced resistant mutant can give some positive indication of the likely development of resistance, as for example in the control of Phytophthora megasperma f.sp. medicaginis by metalaxyl (6). Such mutants cannot be produced in relation to durable fungicides such as... 

Photolytic cleavage at the anomeric center of glycosides as an analytical or preparative tool does not have a very extensive literature. It has, however, been found useful in the solid-phase synthesis of oligosaccharides. Thus the synthesis by Nicolaou and coworkers of the phytoelicitor heptasaccharide of Phytophthora megasperma (Section V) depends on detachment of the protected heptasaccharide from the support by photolytic cleavage of a 4-nitrophenoxy link to the polystyrene polymer. 

Among the polysaccharide elicitors are 3,6-3-glucans from Phytophthora megasperma (84, 85) and yeast cell walls (59) and the algal glucan, laminarin (84)., which have structures comparable to those described for the wilt-inducing P. cinnamomi,... 

A number of factors have been studied for their influence on nicotine production. Of these the negative effect of auxins, and in particular 2,4-D, on alkaloid production is worth mentioning (202-204,211,220, 225,226,229,255). In root cultures the addition of indoleacetic acid (lAA) also reduces alkaloid production (196). Light was reported to inhibit nicotine formation (50,255). In a green cell suspension, however, increased nicotine levels were found on illumination (229). Ikemeyer and Barz (243) reported that a photoautotrophic cell line of N. tabacum did not produce nicotine, whereas a heterotrophic cell line did accumulate this alkaloid. Elicitation with a preparation of the fungus Phytophthora megasperma did not affect the nicotine levels of these cell lines. Addition of organic acids to the medium resulted in increased alkaloid formation in callus cultures (up to 3.25%) (230). For a review of the various cultural factors which influence secondary metabolism, the reader is referred to Mantell and Smith (255). 

Phytophthora megasperma, an often used elicitor, and chitosan were not active on these cultures. On the other hand, polypeptide antibiotics, like polymyxin B, were found to be the most active elicitors. The yeast extract elicitor was tested on callus cultures of 190 different plant species from 25 families. The strongest effects were found in seven species and subspecies of Eschscholtzia, Chelidonium majus, Glaucium rubrum, G. flava, Cory-dalis ophiocarpa, and Papaver somniferum, and in all cases the production of the quaternary phenanthridine alkaloids was induced, as easily recognized by the red coloration of the cultures. 

The stem and root-infecting pathogen of soyhcdja, Phytophthora megasperma, excretes glycoproteins. They have proved to be poor, non-specific elicitors of phytoalexin accumulation. 

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