MAPPING COMPLEMENTARY GENES IN MAIZE - POSITIONING THE RF1 AND RF2 NUCLEAR FERTILITY RESTORER LOCI OF TEXAS (T) CYTOPLASM RELATIVE TO RFLP AND VISIBLE MARKERS

There are three major groups of cytoplasmic male-sterile cytoplasms in maize; C (Charrua), S (USDA), and T (Texas). These cytoplasms can be classified by the unique nuclear genes that suppress the male-sterilit y effects of these cytoplasms and restore pollen fertility. Typically, plants that carry Texas (T) cytoplasm are male fertile only if they c arry dominant alleles at two unlinked nuclear restorer loci, rf1 and r f2. To facilitate analysis of T-cytoplasm-mediated male sterility and fertility restoration, we have mapped rf1 and rf2 relative to closely- linked RFLP markers using five populations. The rf1 locus and/or linke d visible markers were mapped in four populations; the rf2 locus was m apped in two of the populations. Data from the individual populations were joined with the aid of JoinMap software. The resulting consensus maps place rf1 between umc97 and umc92 on chromosome 3 and rf2 between umc153 and sus1 on chromosome 9. Markers that flank the rf1 and rf2 l oci have been used to identify alleles at rf1 and rf2 in segregating p opulations. These analyses demonstrate the possibility of tracking sep arate fertility restorer loci that contribute to a single phenotype.