Associating SSR markers with soybean resistance to iron deficiency chlorosis

Iron deficiency chlorosis (IDC) causes soybean yield loss to growers when certain varieties are planted on calcareous soils. Planting IDC-resistant varieties is the best management practice, although they may still exhibit chlorosis under certain environmental conditions. Environmental variation for chlorosis expression impedes progress in improving IDC resistance. Breeders could use molecular marker-assisted selection (MAS), an environment-independent tool, to improve soybeans' resistance to IDC. Our objective was to determine the efficiency of simple sequence repeat (SSR) markers in selecting for IDC resistance in soybean. A breeding population was developed using parents differing in IDC resistance and yield potential. The population was advanced to the F-2 and F-2:4 generations. Foliar chlorosis data were recorded for parents and F-2:4 lines in replicated field tests planted on calcareous soils at two Iowa locations in 2000 and 2001. Chlorosis scores between parents and F-2:4 lines varied according to location and year. Genotypic data were obtained on individual F-2 plants, and association between chlorosis scores and allele segregation was tested by single-factor analysis of variance using 2001 data. Three SSR markers were associated (P < 0.1) with chlorosis scores at each location; however, the identity of the markers associated with chlorosis scores was different at each location. In addition, two SSR markers associated with IDC resistance were examined for their efficacy in improving breeding efficiency. Preliminary data presented herein demonstrate the importance of environment on expression of this soil-stress factor and the potential of using SSR markers as an environment-independent selection tool for breeding IDC resistance in soybean.