Genetic Mapping of Quantitative Trait Loci Conditioning Protein Concentration and Quality, and Other Seed Characteristics in Soybean [Glycine max (L.) Merrill]

Soybean [Glycine max (L.) Merr.] is grown for its high oil and protein concentration, which may be used in a wide array of industries throughout the world. It contributes about 15 billion dollars annually to the US economy. Focusing on protein concentration and quality, I was interested to discover genomic regions as quantitative trait loci (QTL) associated with nitrogen accumulation during reproductive stages, protein concentration, storage protein fractions, amino acid composition, seed size, oil content, and agronomic traits. A population of 101 F₆-derivedrecombinant inbredlines (RIL) created from a cross of N87-984-16 x TN93-99 were used to achieve these objectives. Experiments were conducted in six environments during 2002 and 2003. A significant (P<0.05) difference among genotypes was found for all agronomic and seed composition traits. A total of 94 polymorphic simple sequence repeat (SSR) molecular genetic markers were screened in DNA from progenies. Single factor ANOVA in SAS software was used to identify candidate QTL that were confirmed by composite interval mapping using QTL Cartographer. QTL governing nitrogen accumulation in soybean seed were distributed among seven linkage groups. Two QTL for protein concentration, seven QTL for oil concentration and eight QTL for seed size were identified. Moreover, three QTL for glycinin (near Satt461, Satt292 and Satt156) and two QTL for conglycinin (near Satt461 and Satt249) were detected in this population. Nine QTL (near Satt002, Satt185, Satt201, Satt235, Satt252, Satt268, Satt427, Satt436 and Satt590) distributed on six molecular linkage groups were associated with cysteine (Cys) and four QTL (near Satt002, Satt252, Satt564 and Satt590) distributed on four molecular linkage groups were associated with methionine (Met) concentration in soybean seed. At least one QTL for each amino acid was detected in this population. Two QTL each for lodging, plant height and seed filling period, six for maturity and three for yield were detected in this population. Three lines developed from this population were released as germplasm by the Tennessee Agricultural Experiment Station. TN03-350 and TN04-5321 were released because those lines combine high yield and increased protein concentration. TN04-5363 was released because it combines high yield and total sulfur containing amino acids (Cys and Met). The QTL identified and the germplasms developed from this study may be useful in improving the nutritional quality of soybean.