Inter-Relations of Growth and Cropping in Apple Trees Studied by the Method of Component Analysis

Abstract

Pomological records taken on Cox’s Orange Pippin and Worcester Pearmain were converted to new variates by the method of component analysis. The new variates, which were the weighted sums of the old, were expressions of physiological characteristics such as vigour, fruitfulness (or intensity of cropping) and apical dominance. A study of the new variates showed that vigour was correlated from year to year, but the correlation decayed with time ; in particular, nursery vigour was little associated with field vigour. A nursery expression of apical dominance was found to be largely associated with nursery position and did not influence later growth and cropping. Later fruitfulness, which showed a tendency to biennial behaviour, was positively correlated with early vigour and negatively related to early severity of pruning. A further variate was determined chiefly by fruit set ; it was associated with field position and with both fruitfulness and fruit set in the previous year.