Control of male fertility using externally inducible promoter sequences

A method of reproducing a plant having heritable, externally controllable male sterility resulting from replacement of a gene which affects flavonol production in the plant with a gene which coats for the same gene product, but which is linked in an expression sequence with an inducible promoter responsive to external control, comprising the steps of:

• a) planting seed of the plant to provide growing, male sterile plants;
• b) inducing conversion of the growing plants to male fertile form by growing the plants under conditions which induce the promoter to express the gene coding for the same flavonol gene product;
• c) open-pollinating the growing plants in isolation to produce seed;
• and
• d) harvesting the seed.

A method of producing hybrid seed, comprising the steps of

• a) planting, in cross pollinating juxtaposition, a first seed from a selected male fertile male parent line and a second seed from a selected female parent line having male sterility resulting from replacement of a gene which affects flavonol production with a gene which affects flavonol production linked in an expression sequence with an inducible promoter responsive to external control,
• b) growing the seed to mature plants under conditions which do not induce expression of the gene;
• c) cross pollinating the male sterile female plant with pollen from the male-fertile male plant;
• and
• c) harvesting hybrid seed from the male-sterile female plant.