Potato scab

Davis, J.G., Callihan, R.H., Effects of gypsum, sulfur, terractor, and terractor super-x for potato scab control. Am Pot J 1974 51 35-43. 

Oestergaard, S.P., Nielsen, S. Control of potato scab (Streptomyces scabies) by irrigation. Tidsskrift for Planteavl 1979 83 201-204. 

Disease control by green manure is an artificial application of allelopathy. Isothiocyanates released from cruciferous plants are an example of this allyl isothiocyanate (166), which is derived from the glucosinolate sinigrin (167), is the most popular example.98 Application of Geranium carolinianum for the control of Ralstonia solanacearum, the cause of bacterial wilt of potato, and potato scab, which is induced by some Streptomyces spp., was reported.99 100 One of the antibacterial constituents was shown to be ethyl gallate (168).101... 

Other putative CKX genes and gene fragments have been found in gene databases of phytopathogenic bacteria, such as Streptomyces spp. [99] causing potato scab, Legionella pneumophila and cyanobacterium Anahaena variabilis (Frebortova, unpublished). 

Previous mention was made of the success obtained in the control or partial control of potato scab and take-all disease of wheat by the addition of green manures. Considerable success has also been obtained in the curtailment of Phymatotrichum root rot of cotton. More recent additions to the list are root- and foot-rot diseases of snap beans caused by Rhizoctonia solani and by Fusarium solani f phaseoli, respectively. The effectiveness of control of these diseases depends on many factors, especially the soil and the organic amendment added. 

The addition of green manures to soils has been shown to effect control or partial control of a number of plant diseases. These include potato scab, take-all disease of wheat, and root rot of cotton and of snap beans. This method is not always successful and many factors, which are not well understood, affect the results. This subject is discussed in Chapter 19. 

During a survey of actinobacteria known to suppress the growth of Streptomyces scabies, the causative agent of potato scab disease, a series of six new phenazine alkaloids were isolated and characterized by Salomon and coworkers [95]. NMR analysis of the ethyl acetate and butanol extracts of the culture supernatant and mycelium suggested a suite of aromatic compounds that were ultimately determined to be glycosylated 1,6-disubstituted phenazines (107—112). The structure of the phenazine and the various substituents that were substituted at the 1- and 6-positions are shown below. The structures of these phenazines, with the exception of 111, are the first examples of diglycosylated phenazine alkaloids. 

Figure 1. Structures of phytotoxins produced by Streptomyces species causing potato scab.

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