Molecular Mapping Genes Conditioning Reduced Palmitic Acid Content in N87-2122-4 Soybean Zenglu Li, Richard F. Wilson, Warren E. Rayford, and H. Roger Boerma* ABSTRACT et al., 1994). Previous studies have shown that reduced palmitic acid was conferred by at least two loci (Erickson Palmitic acid is one of the two major saturated fatty acids of et al., 1988a; Fehr et al., 1991; Wilcox et al., 1994), soybean [Glycine max (L.) Merr.] oil that is closely related to nutri- tional quality of soybean oil. Reduction of palmitic acid content would and no maternal effects were observed (Schnebly et al., lower the total saturated fatty acid content of soybean oil and improve 1994). The alleles conferring reduced palmitic acid from the oil quality for human consumption. Several mutant lines with C1726( fap1) and A22( fap3) are at independent loci (Er- reduced palmitic acid content have been developed in which the genes ickson et al., 1988b; Schnebly et al., 1994). Allelism conditioning palmitic acid content are located at different loci. The studies for the lines C1726, N79-2077-12, and N90-2023 objective of this research was to map the genes conferring reduced indicated that reduced palmitic acid alleles in N79-2077- palmitic acid from N87-2122-4 on the public soybean genetic linkage 12 and N90-2023 segregated independently of the fap1 map with simple sequence repeat (SSR) markers. Four near-isogenic allele in C1726 (Wilcox et al., 1994). However, the genes lines with normal and reduced palmitic acid content and the F 2 and conditioning palmitic acid in N79-2077-12 and N90-2023 F 2:3 generations of a population derived from the cross of ‘Cook’  have not been assigned gene symbols. It was reported N87-2122-4 were used to perform the SSR mapping of the genes conditioning reduced palmitic acid. The results indicated that a major that the genes conditioning reduced palmitic acid in gene with an allele for reduced palmitic acid contributed by N87- N87-2122-4 were inherited from N79-2077-12 (Burton 2122-4 is located near the top of Linkage Group (LG) A1. A SSR et al., 1994; Wilcox et al., 1994), and the reduced palmitic marker, Satt684 in that region accounted for 38% of variation in acid content in N87-2122-4 was conditioned by a major palmitic acid content in the F 2 generation and 31% of variation in the gene and a genetic modifier (Rebetzke et al., 1998). F 2:3 generation. On LG-M, Satt175 accounted for 8% of the variation in N87-2122-4 is an important source of reduced palmitic the F 2 and 9% of the variation in the F 2:3 generation. This minor gene acid genes being used by soybean breeders. Previous on LG-M had a significant interaction with the gene on LG-A1 in studies indicated that genes modifying the major pal- the F 2 generation. When combined in a multiple regression equation, mitic acid loci could influence the genetic variation of these markers explained 51% of total phenotypic variation for palmitic palmitic acid content by increasing or reducing the pal- acid content in the F 2 and 43% of the variation in the F 2:3 generations. mitic acid content (Horejsi et al., 1994; Rebetzke et al., 1998). Modifier genes have been shown to influence S oybean oil is an important source of vegetable oil palmitic acid by 2 to 23 g kg -1 (Horejsi et al., 1994). for human food and nonfood applications and ac- Understanding function and genomic location of genetic counts for approximately 22% of the world’s total edible modifier genes would be useful to breeders in devel- oil production (Glaudemans et al., 1998). Soybean oil oping effective selection schemes to further reduce or consists mainly of palmitic (C16:0), stearic (C18:0), oleic stabilize the palmitic acid content in soybean. (C18:1), linoleic (C18:2), and linolenic (C18:3) acid. Pal- Recent advances in molecular marker technology, es- mitic acid is one of the two major saturated fatty acids pecially the development of SSR markers in soybean of soybean oil and is closely related with physical, chemi- and an integrated soybean genetic linkage map, have cal, and nutritional qualities (Wilson, 1991). The average made possible the genetic mapping and dissection of palmitic acid content in the soybean seed oil of common qualitative and quantitative traits in soybean (Cregan cultivars is 120 g kg -1 (Erickson et al., 1988a; Fehr et et al., 1999). The SSR markers are highly amenable for al., 1991; Burton et al., 1994). Reduction of palmitic automation and allele sizing which can provide for their acid content of soybean oil would lower the total satu- use in high-throughput application and multiple trait rated fatty acid content and improve the oil quality for selection (Diwan and Cregan, 1997; Mitchell et al., human consumption. 1997). Using restriction fragment length polymorphism The manipulation of soybean oil quality by altering (RFLP) makers, Nickell et al. (1994) mapped fap2, an fatty acid composition is an important breeding objec- allele conferring elevated palmitic acid content from tive in the USA (Wilson et al., 1981; Topfer et al., 1995). C1727 on LG-D of the public genetic linkage map Soybean lines with reduced palmitic acid content have (Cregan et al., 1999). Brummer et al. (1995) mapped been developed through chemical mutagenesis, recur- the fan allele controlling reduced linolenic acid from rent selection, and hybridization (Erickson et al., 1988a; C1640 on LG-B2. With a mapping population formed Bubeck et al., 1989; Wilcox and Cavins, 1990; Burton from Glycine max  Glycine soja Siebold & Zucc., Diers and Shoemaker (1992) mapped quantitative trait loci Z. Li, and H.R. Boerma, Dep. of Crop and Soil Sciences, 3111 Miller (QTL) conditioning five major fatty acids mainly on Plant Sciences Building, Univ. of Georgia, Athens, GA 30602; R.F. two linkage groups of the USDA/ISU map using RFLP Wilson, USDA-ARS and North Carolina State Univ., Raleigh, NC markers. The objective of this study was to map the 27607; and W.E. Rayford, USDA-ARS, National Center for Agricul- tural Utilization Research, Peoria, IL 61604. Received 23 April 2001. Abbreviations: GLM, general linear model; LG, Linkage group; QTL, *Corresponding author (rboerma@arches.uga.edu). quantitative trait loci; RFLPs, restriction fragment length polymor- phisms; SSRs, simple sequence repeats. Published in Crop Sci. 42:373–378 (2002). 373