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Effect of leaf age and inoculum concentration on the symptoms produced by Gymnosporangiumjuniperi‐virginianae on apple
Author(s) -
ALDWINCKLE H. S.
Publication year - 1975
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1975.tb01615.x
Subject(s) - biology , cultivar , inoculation , rust (programming language) , shoot , botany , horticulture , lesion , psychology , psychiatry , computer science , programming language
SUMMARY Gymnosporangium juniperi‐virginianae , the incitant of cedar apple rust, induced the greatest number of lesions (flecks, pycnial lesions, aecial lesions) on 6‐ and 8‐day‐old leaves of single‐shoot potted apple plants inoculated and incubated under controlled conditions. The largest pycnial lesions developed on 2‐ and 4‐day‐old leaves and the largest aecial lesions on 6‐day‐old leaves. The number of lesions was positively correlated with the concentration of basidiospores in the inoculum, but lesion size was constant at different inoculum levels. Elevated inoculum concentrations failed to induce pycnia on cv. McIntosh which normally bears only flecks; very low concentrations induced the development of pycnia but not aecia on cv. Rome Beauty, which normally bears aecia. An ‘infection rating’, log 10 (10 nd 2 ), where n is the highest number of pycnial lesions per leaf and d is the largest mean diameter of pycnial lesions on any leaf, calculated for four cultivars in greenhouse tests showed a positive correlation with a ‘susceptibility rating’ developed from observations of natural infection of these cultivars in the field.