Hybrid lettuce plant with a male sterile genotype is heterozygotic for a gene conferring a detectable phenotype. Independent claims are also included for: (1) seed from which the plant is grown； (2) cell of the plant； (3) use of dipterous insects to pollinate male sterile lettuce plants with male fertile plants in a closed environment； (4) producing hybrid lettuce seeds growing male sterile parent plants and male fertile parent plants in close proximity in a closed environment, where one of the parent is homozygotic for a gene conferring a detectable phenotype, effecting pollination by introducing dipterous insects into the closed environment at flowering time in an amount of at least 100 insects/m 2>；, and harvesting seeds produced by the male sterile plants.
