Abstract
Using molecular markers in soybean [Glycine max (L.) Merr.] has lead to the identification of major loci controlling quantitative and qualitative traits that include: disease resistance, insect resistance and tolerance to abiotic stresses. Yield has been considered as one of the most important quantitative traits in soybean breeding. Unfortunately, yield is a very complex trait and most yield quantitative trait loci (QTL) that have been identified have had only limited success for marker assisted selection (MAS). The objective of this study was to identify QTL associated with soybean seed yield in preliminary yield trials grown in different environments and to evaluate their effective use for MAS using a yield prediction model (YPM), which included epistasis. To achieve this objective, 875 F5:9 recombinant inbred lines (RIL) from a population developed from a cross between two prominent ancestors of the North American soybean (Essex and Williams 82) were used. The 875 RIL and check cultivars were divided into four groups based on maturity and each group was grown in Knoxville, TN and one other location that had an environment in which the maturity group (MG) was adapted to be grown. Each RIL was genotyped with >50,000 single nucleotide polymorphic markers (SNPs) of which 17,232 were polymorphic across the population. Yield QTL were detected using a single factor (SF) analysis of variance (ANOVA) and composite interval mapping (CIM). Based on CIM, 23 yield QTL were identified. Twenty-one additional QTL were detected using SF ANOVA. Individually, these QTL explained from 4.5% to 11.9% of the phenotypic variation for yield. QTL were identified on all 20 chromosomes and five of the 46 QTL have not been previously reported. This study provides new information concerning yield QTL in soybean and may offer important insights into MAS strategies for soybean.
Highlights
Cultivar improvements in yield have allowed the soybean [Glycine max (L.) Merr.] to become the most important source of vegetable protein and oil in the world and the second most important crop in the U.S In 2012, the estimated seed yield of soybean in the U.S was 82 million metric tons harvested from 31.2 million hectares of land (Soy Stats, 2013)
The maturity ranged from an early maturity group (MG) III to a late MG III in Group A, which is more adapted to the latitude of Wooster, OH than Knoxville, TN (Sleper, 2006)
This study suggests that environment specific data continues to be valuable and that while marker assisted selection (MAS) can successfully predict high yielding lines, it might miss some of the very top yielding lines unless the prediction equation includes data from the environment in which the yield trial is conducted
Summary
Cultivar improvements in yield have allowed the soybean [Glycine max (L.) Merr.] to become the most important source of vegetable protein and oil in the world and the second most important crop in the U.S In 2012, the estimated seed yield of soybean in the U.S was 82 million metric tons harvested from 31.2 million hectares of land (Soy Stats, 2013). Sebastian (2010) and Hyten et al (2006) showed that current selection procedures are not efficient in exploiting the available genetic diversity. Using MAS for yield could increase breeding efficiency, and would improve our understanding of the genetic mechanisms of seed yield. There has been an increased interest in MAS, very few yield QTL in soybean have been validated across a wide range of environments and populations. Sebastian et al (2010) used context-specific MAS (CSM) to detect yield QTL in elite soybean cultivars. Significant yield gains of up to 5.8% were confirmed and two of the improved sublines were released as improved cultivars
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