In Shepherd's Purse, the fruit shape is controlled by
A.Supplementary genes – Two indepednet pairs of genes, which interact to produce a new trait together, but each dominant gene alone produces its own trait, are called Supplementary genes. eg: comb types in chickens
B.Complementary genes – Two independent pairs of genes, which interact to produce a trait together, but each dominant gene alone does not show its effect, are called complementary genes. eg: flower colour in Lathyrus
C.Duplicate genes – If the dominant alleles of two genes loci produce the same phenotype. eg:capsule of Sheperd’s purse.
D.Polymeric genes - Two independent dominant genes, whether present in homozygous or heterozygous condition, have similar phenotypic effect when present individually but produce a cumulative or double effect when found together. Eg:flower colour of Lathyrus
So, the correct option is ‘Duplicate genes’.