RECOVERY OF HERITABLE, TRANSPOSON-INDUCED, MUTANT ALLELES OF THE RF2 NUCLEAR RESTORER OF T-CYTOPLASM MAIZE

T (Texas) cytoplasm is associated with a mitochondrial disruption that is phenotypically expressed during microsporogenesis resulting in mal e sterility. Restoration of pollen fertility in T-cytoplasm maize is c ontrolled by dominant alleles at two unlinked, complementary, nuclear- encoded genes, rf1 and rf2. As a first step in the molecular isolation of the rf2 gene, 178,300 gametes derived from plants that carried the Mutator, Cy or Spm transposon families were screened for rf2 mutant a lleles (rf2-m) via their inability to restore pollen fertility to T-cy toplasm male-sterile maize. Seven heritable rf2-m alleles were recover ed from these transposon populations. Pedigrees and restriction fragme nt length polymorphism (RFLP)-based analyses indicated that all seven rf2-m alleles were derived independently. The ability to obtain rf2-m derivatives from Rf2 suggests that Rf2 alleles produce a functional pr oduct necessary to restore pollen fertility to cmsT. Molecular markers flanking the rf1 and rf2 loci were used to decipher segregation patte rns in progenies segregating for the rf2-m alleles. These analyses pro vided preliminary evidence of weak, third restorer gene of cmsT that c an substitute for Rf1.