Inability of a plant to produce fertile pollen

Male sterile plants have been genetically engineered to produce no (fertile) pollen. The idea is to prevent transgenes from out-crossing into conventional plants. The major problem with developing male sterile plants is the fact that most crops need pollination to produce fruit. One solution can be to supply transgene-free pollen for fertilisation by planting quantities of conventional, fertile crops in a field of male sterile GM crops.