Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2001
Publication Date: N/A
Citation: Interpretive Summary: Continued productivity of the hybrid grain sorghum in the U.S. is dependent on the efficient production of hybrid seed through the use of cytoplasmic male sterility (CMS). Many sources of CMS are available, but their utilization is in part dependent on efficient identification of fertility restorer genes for use in breeding. Scientists at the Center for Agricultural, Medical and Veterinary Entomology in the Crop Genetics and Environmental Research Unit in Gainesville, Florida, and ARS scientists at the Southern Plains Agricultural Research Center in College Station, Texas, have isolated and developed molecular markers for one such gene, designated Rf4. Using contemporary molecular genetic marker development systems and genome technologies, three molecular markers, one very close to the Rf4 gene, have been identified. Utilization of these markers will allow geneticists and breeders to rapidly introgress the gene into agronomically important germplasm, and will allow rapid progress towards recovering and identifying the Rf4 gene and the mechanism through which it participates in promoting normal pollen development.
Technical Abstract: The restoration of male fertility in the sorghum IS1112C (A3) male-sterile cytoplasm is through a gametophytic system involving complementary action of two genes, designated Rf3 and Rf4. To develop markers suitable for mapping rf4, AFLP technology was applied to bulks of sterile and fertile individuals from a segregating BC3F1 population. Three AFLP markers linked to rf4 were identified and subsequently converted to STS/CAPS markers, two of which are co-dominant. Based on a population of 378 BC1F1 individuals, two STS/CAPS markers, LW7 and LW8, mapped to within 5.31 and 3.18 cM, respectively, of rf4, while an STS marker, LW9, was positioned 0.79 cM on the flanking side of rf4. Markers LW8 and LW9 were used to screen sorghum BAC libraries to identify the genomic region encoding rf4. A series of BAC clones shown to represent a genomic region of linkage group E were identified by the rf4-linked markers. A contig of BAC clones flanking the LW9 marker represent seed clones on linkage group E from which fine mapping of the rf4 locus and chromosome walking can be initiated.