A biometrical investigation has been made of the behaviour and inter-relations of the more important quantitative characters in selfed, sibbed and backcrossed families of raspberries (Rubus idaeus L.). Plant characters analysed were height, vigour, spine intensity, mildew susceptibility and vegetative bud break; inbreeding depression particularly affects height and mildew susceptibility. Flowering and fruiting characteristics included flowering ability, fruit colour, first-year fruiting ability, time of ripening and maturity rate. Some families segregated for double bearing.
Fruit qualities, including size, shape and texture, were assessed: heterosis may influence size, but large fruited inbreds are obtainable. The conical shape may be associated with advantageous fruit qualities. Texture depends partly on ability of drupelets to adhere and not to collapse under slight pressure; these two qualities are not necessarily correlated. There are no correlations between fruit size, or plug shape, with ease of picking.
Flavour was assigned organoleptically to five classes. Backcrossing to a quality flavoured clone increased the frequency of good flavoured seedlings and reduced that of acidy types, but segregations for all classes occurred in sibs, selfs and back- crosses. Taste trials showed that people are generally agreed on the flavour they least like, but are unreliable in their preference. Commercial raspberry improvement should therefore be in the hands of several independent breeders.
Thirty-six seedlings with the best “all-round” biometrical assessments, out of a total population of 841, were tested for yield over two years; two died in the first winter. Twenty-one seedlings had higher yields, four had the same and nine had less than their controls. Hence such an assessment is of value in assorting out the potentially higher yielders from the bulk of a breeding population.