Identification of Novel Quantitative Trait Loci for Soybean Seed Oil, Protein, Size and Coat Color Using SSR and SNP Markers.

Soybean contains 20% oil and 40% protein on a seed dry weight basis and 27.2 kg (a 60-pound bushel) of soybean yields about 21.8 kg (48 pounds) of protein-rich meal and 5 kg (11 pounds) of oil. US is the leading soybean producer and exporter and in 2008, soybean and soybean products exports exceeded $20 billion. Importers need at least 19% oil and 35% protein for soybean-meal and oftentimes they offer premiums for soybean containing higher amounts of oil and protein. In the last two decades, soybean yield has increased significantly with no significant changes in oil and protein contents. Yield is inversely related to protein, oil and protein are also inversely related and that makes it difficult to improve both traits simultaneously. Molecular markers may be helpful to identify quantitative trait loci (QTL) controlling oil and protein contents and may be used in marker-assisted breeding. Soybean seed oil and protein QTL have been mapped in different mapping populations. In most cases, mapping populations were smaller sizes and used limited number of molecular markers. Objectives of this study were to identify novel QTL in a mapping population using a larger number of molecular markers. Two-hundred and fifty F₇ recombinant inbred lines (RILs) were randomly chosen from 1000 lines developed from a cross between Magellan, a high yielding soybean cyst nematode (SCN) susceptible genotype, with yellow seed coat, higher oil and lower protein and PI438489B, a SCN resistant line with black seed coat, lower oil and higher protein. These RILs were evaluated in replicated trials at three diverse environments in Missouri during summer 2007 and 2008. Seed oil and protein were quantified using Near-infrared Reflectance spectroscopy (FOSS NIR, model 6500). About 800 polymorphic SSR and SNP markers were used for genotyping. Genetic map construction and QTL analysis are in progress.