Use of recessive homozygous genotypes to assess genetic control of kernel bitterness in almond

Bitter flavour of the almond kernel is due to the cyanoglucoside amygdalin and has been the first characteristic considered in breeding programmes. In such programmes, the seedlings from sweet-kernelled parents were used to study the transmission of bitterness, which was shown to be a monogenic characteristic, the sweet flavour being dominant. The aim of this work was to investigate more deeply the inheritance of bitterness in almond, by studying for 2 consecutive years the bitter flavour in 169 seedlings of 9 families (obtained exclusively for this purpose), one or both parents being bitter-kernelled. With the exception of the presence of slightly bitter seedlings, the results support the hypothesis of monogenic inheritance of this trait, the bitter flavour being recessive, although other factors could have a slight influence on the expression of this characteristic. Heterozygous individuals showed sweet, slightly bitter or year-changeable (sweet-slightly bitter) phenotypes. Our results demonstrated the possibility of using as parents bitter-kernelled individuals with some outstanding characteristic desirable for transmission to the progeny, always in combination with a homozygous sweet progenitor.