A quantitative study of the course of fungal invasion of the apple fruit and its bearing on the nature of disease resistance.—Part I. A statistical method of studying fungal invasion

Abstract

A study of approximately 15,000 inoculations of apples with fungi, the invasion of which was observed during various periods of storage life, and at different temp., demonstrated that "radial advance" gave the most accurate measure of damage done and the degree of resistance. Radial advance denotes the distance from the point of inoculation to the front of the invasion, expressed in fractions of the radius (of the apple). Use of this factor avoids the complex relations which hold between weight of rotted material and the penetration of the fungus, the standard error of the mean of radial advance being less than 1/2 that of percentage weights. It is also shown by the high positive correlation between radial advance on opposite sides of individual apples, and by the correlation obtained from 2 successive inoculations of the same individual by the same fungus, that each apple has a characteristic resistance.