Genetics of resistance to <i>Amphorophora rubi</i> (Kalt.) in the raspberry II. The genes <i>A</i>₂–<i>A</i>₇ from the American variety, Chief

Abstract

The American raspberry variety Chief is shown to carry three dominant genes, A 5 , A 6 and A 7 , each capable of conferring strong resistance to Amphorophora rubi strain 1. Chief also carries three genes, A 2 , A 3 and A 4 , for resistance to A. rubi strain 2. A 2 is a dominant gene conferring full resistance by itself; A 3 and A 4 are dominant complementaries, neither gene by itself having any effect on resistance. A 5 is linked with either A 3 or A 4 with a crossover value of 10%. The gene A 1 from Baumforth A, which confers resistance to strains 1 and 3, when combined with A 3 gives resistance to strain 2 also. Thus the three strains of A. rubi at present recognized on raspberries in Britain can be controlled by using either the combination A 1 A 2 or A 1 A 3 .