SUMMARY: Extracts of the polyphenolic fractions of the water-soluble metabolites (that is, the complex mixtures of plant phenols extracted by ethyl acetate) were prepared from apple and pear varieties characterized by different degrees of resistance to the scab pathogens. Qualitative differences were chiefly interspecific and extracts of resistant varieties did not contain major components lacking in those of less-resistant varieties of the same species. Cultural reactions of distinct clones of each pathogen to the extracts, in the presence of various basal media, were observed. Growth and sporulation were inhibited independently by extracts of less-resistant as well as resistant host varieties. The clones were not equally susceptible, those of showing relationships between inhibition of sporulation by host polyphenols and their varietal host ranges. Fluctuations in pathogenicity of a clone of during storage in culture with periodic re-isolation from Williams pear were reflected in its reactions to the extracts. Both pathogens were capable of decomposing the polyphenols. The results suggested that qualitative and quantitative variations in the polyphenolic host metabolites, including differences in their relative proportions, in relation to nitrogenous and other nutritional factors, are of potential significance in the determination of pathogenicity and varietal resistance.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error