Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2009
Publication Date: 8/1/2009
Citation: Klein, M.A., Grusak, M.A. 2009. Identification of nutrient and physical seed trait QTLs in the model legume, Lotus japonicus. Genome. 52:677-691. Interpretive Summary: Legume seeds have the potential to provide a significant portion of essential macro- and micronutrients to the human diet. Because we would like to develop tools to breed more nutritious legumes, it is important that we identify the genetic basis for seed nutrient density. One way to gain this information is to use special populations of plants that have defined genetic characteristics. In this study, we used one such population of the model legume Lotus japonicus and harvested seeds in order to analyze seed mineral concentrations and seed weight. Statistical tests of the mineral concentration and weight results allowed us to identify specific regions within the plant's DNA that are associated with genes that contributed to high levels of seed minerals or elevated seed weight. These results will allow us to identify specific genes that could lead to nutritionally improved crops or increased seed yield, especially in agronomically important legumes.
Technical Abstract: Legume seeds have the potential to provide a significant portion of essential micronutrients to the human diet. To identify the genetic basis for seed nutrient density, quantitative trait locus (QTL) analysis was conducted with the Gifu B-129 x Miyakojima MG-20 recombinant inbred population from the model legume Lotus japonicus. This Lotus population was grown to seed under greenhouse conditions in 2006 and 2007. Phenotypic data were collected for calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P), sulfur (S), and zinc (Zn) seed concentrations and content. Physical seed trait data (average seed weight and seed-pod allocation values) were also collected. Based on these phenotypic data, QTL analyses identified 92 QTLs linked to 51 different molecular markers. Transgressive segregation, identified within these RILs for both seed nutrient and physical traits, suggests new allelic combinations are available for agronomic trait improvement. QTL colocalization was also seen, suggesting that common transport processes might contribute to seed nutrient loading. Identification of loci involved in seed mineral density can be an important first step in identifying the genetic factors and consequently, the physiological processes involved in mineral distribution to developing seeds. Longer-term research efforts will focus on facilitating agronomic breeding efforts through ortholog identification in related crop legumes.