METHOD OF HYBRID SEED PRODUCTION USING CONDITIONAL FEMALE STERILITY

The present invention provides a method for hybrid seed production comprising producing a conditional female sterile plant comprising a female-preferential promoter operably linked to a coding sequence which encodes an enzyme which catalyzes the conversion of a protoxin to a toxin, interplanting the conditional female sterile plant with a male sterile plant, applying the protoxin to the conditional female sterile plant, and producing hybrid seed. Viable seed formation is prevented on the conditional female sterile plant as a result of the conversion of the protoxin to the toxin in the female reproductive structures, and pollen production is prevented on the male sterile plant, thus allowing interplanting of the two parents of the hybrid cross in order to provide more efficient pollen transfer. Also provided are expression cassettes useful in the invention, plants transformed with the expression cassette, and novel female-preferential promoters.