Spur Type Growth Habit in 60 Apple Progenies1,2

Abstract

Abstract Growth habit at bearing age was studied in 60 progenies of apple, Malus pumila Mill. One progeny, ‘Golden Delicious’ × ‘McIntosh Wijcik’, segregated into 2 distinct growth types, spur-type (compact) and non-spur (standard) at an approximate 1:1 ratio. In the other 59 progenies there was a continuous variation from trees with no or few spurs to trees with many spurs. Trees were classified into 5 arbitrary “spurriness” classes, mainly based on the ratio of spurs to vegetative shoots. Average spurriness of a progeny generally increased with that of its parents. Spur-type mutants of standard cultivars when used as both parents increased the degree of spurriness slightly, but less than expected. Certain progenies had 30 to 56% trees comparable in spurriness to the spur-types of commercial apple cultivars. Among parents inducing spurriness in the progeny, ‘Melba’ was outstanding.