Mid-oleic quantitative trait loci in two soybean crosses

Oleic acid is a major monounsaturated fatty acid that plays a vital role in soybean oil quality. Soybean oil with high oleic acid increases stability at high cooking temperatures and reduces the need for hydrogenation, thus reducing trans-fats. Molecular breeding can be a valuable tool to detect the genomic region of the soybean genome controlling this trait and develop soybean varieties with increased levels of oleic acid content. Although many Quantitative Trait Loci (QTL) have been reported in soybean for oleic acid content, none or very few have been confirmed in other populations from the same or different gene pools. Moreover, there is inconsistent information on the confirmation of previously reported QTL. Previous studies on the oleic acid content in soybean oil have determined the presence of six quantitative trait loci which are clustered in four different linkage groups (A1∼96cM, D2∼85cM, G∼22-53cM, and L∼30-71cM). The objective of this study was to confirm the association of the QTL candidates with oleic acid content and to determine the individual contributions of specific QTL for oleic acid in three types of breeding populations. The plant materials used in the study were derived from 140 F3 lines, 60 BC1F 3 lines, and 90 F5 lines with two replications. All three populations were developed by crossing a South Dakota line, SD01-076R, to a North Carolina germplasm line, N98-4445A, which contained increased levels of oleic acid. Nine microsatellite markers related to the QTL genomic regions were used. Single factor ANOVA (SF-ANOVA) was used to identify candidate QTL. Four QTL (Satt200 on LG-A1 with R2 = 3.5%, Satt235 on LG-G with R2 = 9.4%, Satt303 on LG-G with R2 = 4%, and Satt398 on LG-L with R2 = 4.6%) were confirmed in the F 3 lines. In the BC1F3 lines, two major QTL (Sat113 on LG-L with R2 = 27.3% and Satt235 on LG-G with R2 = 23.8%) and one minor QTL (Satt200 on LG-A1 with R2 = 9.9%) were significantly associated to oleic acid content. For F6 lines, only one significant QTL (Satt235 on LG-G with R2 = 4.1%) was found to be associated with oleic acid content. Based on two-factor ANOVA, there was no significant interaction between the QTL identified in the F3 and F6 lines. Satt235 was consistently associated with oleic acid content across all populations. QTL associated with oleic acid are not stable across populations. The unconfirmed QTL may have been false positive or specific for the original mapping population. This study shows the necessity for confirmation of novel QTL in many different populations and environments. The validation of original QTL will help the efficiency of MAS application in plant breeding programs and facilitate QTL physical map establishment. Future work will include F2:4 population QTL confirmation to further validate the QTL reported and to develop a soybean line with elevated oleic acid content.