SEQUENCE-BASED GENETIC-MARKERS FOR GENES AND GENE FAMILIES - SINGLE-STRAND CONFORMATIONAL POLYMORPHISMS FOR THE FATTY-ACID SYNTHESIS GENES OF CUPHEA

Gene sequences are rapidly accumulating for many commercially and scie ntifically important plants, These resources create the basis for deve loping sequence-based markers for mapping and tracking known (candidat e) genes, thereby increasing the utility of genetic maps. Members of m ost of the gene families underlying the synthesis of seed oil fatty ac ids have been cloned from the medium-chain oilseed Cuphea. Allele-spec ific-PCR (AS-PCR) and single-strand conformational polymorphism (SSCP) markers were developed for 22 fatty acid synthesis genes belonging to seven gene families of Cuphea using homologous and heterologous DNA s equences. Markers were developed for 4 fatty-acyl-acyl carrier protein thioesterase, 2 beta-ketoacyl-acyl carrier protein synthase I, 4 beta -ketoacylacyl carrier protein synthase II, 3 beta-ketoacyl-acyl carrie r protein synthase III, 3 acyl carrier protein, 2 beta-ketoacyl-acyl c arrier protein reductase, and 4 enoylacyl carrier protein reductase lo ci; Eighty-eight percent (14 of 16) of the SSCP loci were polymorphic, whereas only 9% (2 of 22) of the AS-PCR loci were polymorphic. These markers were mapped using a Cuphea viscosissima x C. lanceolata F-2 po pulation and produced linkage groups of 10, 3, and 2 loci (3 loci segr egated independently). The 10-locus linkage group had every gene but o ne necessary for the synthesis of 2- to 16-b carbon fatty acids from a cetyl-CoA and malonyl-ACP (the missing gene family was not mapped). SS CP analysis has broad utility for DNA fingerprinting and mapping genes and gene families.