Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2011
Publication Date: 10/25/2013
Citation: King, K., Peiffer, G., Lauter, N.C., Lin, S., Cianzio, S., Shoemaker, R.C. 2013. Mapping of iron and zinc quantitative trait loci in soybean (glycine max (L.) Merr.) for association to iron deficiency chlorosis resistance. Journal of Plant Nutrition. 36(14):2132-2153. Interpretive Summary: Although iron is the 4th most abundant mineral in the earth's crust it is a major limiting factor to plant growth. This is especially an issue in the upper Midwestern U.S. where soils are calcareous with a high pH. Iron deficiency chlorosis (IDC) causes many millions of dollars of lost production each year. Selecting cultivars that are tolerant to IDC is the best approach to crop improvement. However, selection is very difficult due to the strong influence of the environment and the genetic complexity of the trait. Breeders would greatly benefit from an easier indirect selection method. In this study the authors evaluated a soybean population for IDC, as well as iron and zinc accumulation in seed and leaves. They showed for the first time that regions of chromosomes containing genes affecting response to IDC are the same regions as those affecting iron accumulation in seed. This means that simply measuring iron concentration in seed may provide an indirect indication of the relative iron efficiency of a cultivar. This information is very useful to plant breeders trying to improve the iron efficiency of agronomic lines.
Technical Abstract: Iron deficiency chlorosis (IDC) is a nutritional disease of soybean (Glycine max (L.) Merr.) which when left unchecked can result in a severe yield penalty or even death in the most extreme cases. In order to curb these effects, resistance to the disease is needed. Breeding for resistance has been somewhat successful but no cultivar has complete resistance. Mineral content of the soybean could be an indicator of the ability of the plant to withstand the effects of IDC. Iron and zinc concentration was examined in soybean seed and leaves to be used as an estimator of mineral deficiency resistance in early growing stages of soybean, when symptoms are commonly observed. The progeny (F2:4) of the cross Anoka x A7, previously used to map Fe efficiency QTL, were analyzed to quantify Fe and Zn concentration for QTL mapping and determine if there was a relation to previously identified Fe efficiency quantitative trait loci QTL. Significant differences in Fe and Zn concentration were observed in the progeny population. The range for seed Fe concentration was 67.6 – 92.7 µg/g, and for seed Zn the range was 3.5 – 4.0 µg/g. One hundred-fifty SSR, RFLP, and BARCSOYSSR markers completed the linkage map used for (QTL) mapping of Fe and Zn concentrations. The QTL analysis in the combined data indentified one major QTL for seed Fe accumulation that mapped to chromosome 20 and explained 21.5 % of the variation. Three suggestive QTL were mapped to chromosomes 1 and 12 with chromosome 12 having two peaks. These QTL explained 10.6-12.7 % of the variation. No significant QTL for seed Zn concentration were indentified, however there were two suggestive QTL explaining 18.5 and 23.4 % of the phenotypic variation. The significant QTL for Fe concentration indentified was in the marker interval pa_515-1-Satt239. Marker pa_515-1 was previously used to map a Fe-efficiency QTL and thus provides the first evidence of a potential genetic link between Fe-efficiency and Fe accumulation in the soybean seed.