Male sterility is the failure of the male gametes to be produced viable i.e there is no formation of the viable pollen grains which carry the male gametes in plants. The pollen grain is non-functional but the female gametes function normally. It occurs in nature sporadically, perhaps due to mutation. Male sterility is also due to environmental factors. Male sterility in crop plants is classified in the following types (1) Genetic Male Sterility (GMS) (2) Cytoplasmic Male Sterility (CGMS). (3) Temperature-Sensitive Genetic Male Sterility (TGMS). (4) Chemically-Induced Male Sterility (CIMS). (5) Photoperiod-Sensitive Genetic Male Sterility (PGMS). (6) Transgenic Genetic Male Seterility (Tr.GMS). Wheat improvement by genetic engineering requires the delivery, integration and expression of defined foreign genes into suitable regenerable explants. Initial attempts at introducing transgenes into wheat employed protoplasts as explants due to the absence of cell walls. Initial steps for genetic transformation involves delivery of a gene cassette into recipient cells followed by analysis of the expression of delivered gene. Это и многое другое вы найдете в книге Genetic Male Sterility in Fodder Crops (Qurban Ali,Jehanzeb Farooq and Muhammad Ahsan)