Molecular Marker Satt481 is Associated with Iron-Deficiency Chlorosis Resistance in a Soybean Breeding Population

IDC in soybean has been improved through conventional breeding approaches (Cianzio, 1991; Cianzio and Soybean [Glycine max. (L.) Merr.] breeders have improved resisVoss, 1994; Hintz et al., 1987), IDC-resistant lines may tance to iron-deficiency chlorosis (IDC) using conventional breeding have lower yield potential than IDC-susceptible cultiapproaches; however, many IDC-resistant cultivars have lower yields vars (Fehr, 1982, 1983). compared to IDC-susceptible cultivars. The importance of environment on IDC-resistance expression hinders progress in breeding for Selection for IDC resistance has been based on foliarresistance. An environment-independent selection strategy, such as chlorosis symptoms observed in plantings on calcareous marker-assisted selection (MAS), may increase breeding efficiency. Our soils (Cianzio et al., 1979). Complex polygenic inheriobjective was to determine whether simple sequence repeat (SSR) tance of IDC resistance and genotype environment markers located in previously reported quantitative trait loci (QTL) interactions may result in inaccurate assessment of resisfor IDC resistance would be associated with IDC resistance in a tance, which reduces the value of phenotypic rating and breeding population. One-hundred and eight SSR markers genetically decreases efficiency of breeding to improve the trait linked to eight QTLs on eight molecular linkage groups (MLGs) pre(Lin et al., 2000b). Therefore, if an environment-indeviously identified for IDC were tested in a breeding population evalpendent approach could be devised, there might be the uated for IDC resistance on calcareous soils in Iowa. The breeding potential to improve breeding efficiency for IDC. population was developed from a cross between Pioneer 9254 and A97–770012. The F2 lines were genotyped with markers and the F2– Quantitative trait loci for IDC resistance have been derived lines (F2:4 and F2:5) were evaluated for IDC resistance. Three identified using restriction fragment length polymormarkers were associated with IDC resistance: Satt211, Satt481, and phism (RFLP) markers in two soybean populations in Sat_104. However, of the three markers, only Satt481 was associated field and hydroponic evaluations (Lin et al., 1997, 2000a). to IDC resistance across environments. Although Satt481 accounted Lack of common RFLP markers in the two populations for only 12% of the total phenotypic variation, molecular analysis of prompted Lin et al. (2000b) to conclude that the examthe eleven-most resistant lines in the population indicated that 73% ined molecular markers would be inefficient in MAS. of the lines were homozygous for the resistant allele at the Satt481 Instead, they proposed use of SSR markers due to high locus. Our results indicated that Satt481 may be useful to improve occurrence of polymorphisms and the availability of IDC resistance in this soybean population and that additional QTLs large number of SSR markers in the public domain. conferring resistance to IDC might exist in soybean. The mapping populations used by Lin et al. (1997, 2000a) were developed by using highly IDC-susceptible genotypes crossed to highly IDC-resistant genotypes. I chlorosis of soybean may occur when However, there is no information about the associations certain cultivars are grown on calcareous soils (Froehof QTLs and IDC resistance in actual breeding populalich and Fehr, 1981; Niebur and Fehr, 1981). The cultitions, namely when the parents used in the cross possess vars, unable to acquire and utilize iron efficiently, may a number of desirable agronomic traits along with moddevelop foliar chlorosis, leading to yield loss (Froehlich erate IDC resistance. To simulate a practical breeding proand Fehr, 1981; Niebur and Fehr, 1981). Calcareous soils gram, a population was developed as described above, in the USA are found mainly in the Midwestern portion using parents with intermediate IDC scores and a numof the country, especially Iowa, Minnesota, Nebraska, ber of desirable agronomic traits, to examine the associand South and North Dakota (Franzen and Richardson, ation between QTLs and IDC using SSR markers. Pre2000; Froehlich and Fehr, 1981; Inskeep and Bloom, liminary results from this population, using 1-yr data, 1984; Penas and Wiese, 1990). indicated a possible association between Satt481 and The best method of preventing IDC is to plant IDCIDC resistance (Charlson et al., 2003). On this basis, our resistant cultivars (Fehr, 1982). Although resistance to objective was to continue examining whether SSR markers located in previously reported IDC QTLs would be D.V. Charlson, Dep. of Biochemistry, 109 Life Sci. Ctr., Univ. of Misassociated with IDC resistance in the breeding popusouri, Columbia, MO 65211-7700; T.B. Bailey, Dep. of Statistics, S.R. lation. Cianzio, Agronomy Dep., and R.C. Shoemaker, USDA-ARS, Corn Insect and Crop Genetics Research Unit, Iowa State Univ., Ames, IA 50011. Partial funding given by the Iowa Soybean Promotion Board. MATERIALS AND METHODS This research was undertaken when the senior author was an Interdepartmental Plant Physiology Major at the Iowa State University, Population Development Ames. Received 26 Aug. 2004. *Corresponding author (charlsond@ A breeding population was developed from a cross between missouri.edu). a high-yielding cultivar, Pioneer 9254 (P9254), and an advanced Published in Crop Sci. 45:2394–2399 (2005). Crop Breeding, Genetics & Cytology Abbreviations: H b, Broad-sense heritability; IDC, iron-deficiency chlorosis; MAS, marker-assisted selection; MLG, molecular linkage doi:10.2135/cropsci2004.0510 © Crop Science Society of America group; QTL, quantitative trait loci; RFLP, restriction fragment length polymorphism; SSR, simple sequence repeat. 677 S. Segoe Rd., Madison, WI 53711 USA 2394 Published online October 27, 2005