NUCLEAR MALE STERILE PLANTS, METHOD OF PRODUCING SAME AND METHODS TO RESTORE FERTILITY

The present invention is directed to the production of male sterile plants by providing them with a recombinant DNA capable of specific expression in the male reproductive system of a plant of the enzyme trehalose phosphate (TPP). Resotration of the fertility can be established either by providing said male sterile plants with a recombinant DNA capable of expression of trehalose phosphate synthase (TPS) under control of an inducible promoter or with a recombinant DNA capable of expression of a suppressor protein which suppresses expression of TPP under control of an inducible promoter. This inducible restoration possibilities enable the maintenance of a homozygous male sterile line. Restoration can also be done by spraying the male sterile plants with gibberellic acid. For production of hybrids or hybrid seed a site-specific recombination system is provided, by inserting two site=specific recombination sites flanking the recombinant DNA coding for TPP and crossing the male sterile lines with lines expressing the corresponding recombinase. By crossing the recombinase will excise the gene coding for TPP and fertile hybrids are produced.