Mendelian inheritance of introrse orientated anthers in Brassica rapa

The inheritance of anther orientation of 154 individuals from two B1 populations of Brassica rapa (syn. Brassica campestris) was evaluated under controlled conditions in a greenhouse. The anther orientation was evaluated visually at the time of fully open flowers. The observed extrorse:introrse ratios were 1 : 1 in R-o-18 × (R-o-18 × RM29) population and 3 : 1 in R-o-18 × (R-o-18 × R c-50) population. It was concluded that this trait is controlled by two duplicated pairs of genes (A1, A2) for extrorse anthers, either of which can produce extrorse anthers when a single dominant allele is present. Introrse anthers result when all alleles at both loci are recessive.