|TANG, HOANG - 6615-10-40
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2003
Publication Date: 9/15/2003
Citation: TANG, H.V., PRING, D.R. 2003. CONVERSION OF FERTILITY RESTORATION OF THE SORGHUM IS1112C (A3) MALE-STERILE CYTOPLASM FROM TWO GENES TO ONE GENE. CROP SCIENCE. 43(5):1747-1753.
Interpretive Summary: Hybrid U.S. grain sorghum production is dependent on the use of cytoplasmic male sterility (CMS) for efficient seed production. Many sources of CMS are available, but only one source is used because it is easy to manipulate. An alternative source, the IS1112C source, is not used because F1 hybrids did not produce adequate seed. We determined that the reason for low seed set is that fertility restoration requires two genes, and that only 25% viable pollen is produced in hybrids. DNA markers and molecular analyses enabled us to separate the two genes and incorporate one of the genes into the two parents used for crosses. Test crosses confirmed that the two genes must act in concert to obtain viable pollen, and that subsequent fertility restoration requires only one gene. Thus we have demonstrated that the fertility restoration system can be converted to a single gene. Utilizing this information, the hybrid seed industry can evaluate the feasibility of using this alternative source of CMS for hybrid production.
Technical Abstract: The restoration of male fertility in sorghum lines carrying the IS1112C male-sterile cytoplasm requires complementary gametophytic action of two restoring alleles, Rf3 and Rf4, for individual gamete viability. An F1 heterozygous for the two restoring loci is expected to exhibit 25% viable pollen, and is characterized by limited seed set, which precludes utilization. Single-seed descent B3Tx398/IS1112C F6:5 lines were used to generate homozygosity at the rf3 and rf4 loci, and critical segregants were identified by progeny tests, assays for action of the Rf3 allele, and genomic markers for the rf4 locus. Using these criteria, the genotypes Rf3Rf3rf4rf4 and rf3rf3Rf4Rf4 were constructed in normal, male-fertile cytoplasm lines, and in IS1112C male-sterile cytoplasm lines. Pollination of either male-sterile line with either male-fertile line resulted in about 25% pollen staining in the F1, demonstrating complementation of the two restoring loci. Pollination of either male-sterile line with IS1112C, homozygous at both loci, resulted in about 50% pollen staining. These characteristics substantiate complementary action of the restoring alleles, and are consistent with successful conversion to a single gene fertility restoration system.