The present invention relates to DYAD genes, mutants thereof, and use of them for making plants that retain heterozygosity of the female parent plant. The invention also encompasses plants, plant tissues, and seeds of plants that have a dyad phenotype and so retain heterozygosity of the female parent, either constitutively or conditionally. The invention is useful for propagating desired hybrid phenotypes in a manner of an apomictic plant and for increasing the ploidy of a plant genotype, which may result in plants having increased biomass.