Which blood group is result of homozygous recessive gene interactions?

The inheritance of blood group in human ABO system depends on three alleles of one gene. Two dominant alleles, I ^A and I ^B and one recessive allele, i, make up six combinations of genotype, determining four phenotypes of blood group. Amongst them, the pair of recessive alleles, ii denotes blood group O , which has no surface antigen on RBC.