Conditional QTL mapping of oil content in rapeseed with respect to protein content and traits related to plant development and grain yield

Abstract

Oil content in rapeseed (Brassica napus L.) is generally regarded as a character with high heritability that is negatively correlated with protein content and influenced by plant developmental and yield related traits. To evaluate possible genetic interrelationships between these traits and oil content, QTL for oil content were mapped using data on oil content and on oil content conditioned on the putatively interrelated traits. Phenotypic data were evaluated in a segregating doubled haploid population of 282 lines derived from the F(1) of a cross between the old German cultivar Sollux and the Chinese cultivar Gaoyou. The material was tested at four locations, two each in Germany and in China. QTLMapper version 1.0 was used for mapping unconditional and conditional QTL with additive (a) and locus pairs with additive x additive epistatic (aa) effects. Clear evidence was found for a strong genetic relationship between oil and protein content. Six QTL and nine epistatic locus pairs were found, which had pleiotropic effects on both traits. Nevertheless, two QTL were also identified, which control oil content independent from protein content and which could be used in practical breeding programs to increase oil content without affecting seed protein content. In addition, six additional QTL with small effects were only identified in the conditional mapping. Some evidence was apparent for a genetic interrelationship between oil content and the number of seeds per silique but no evidence was found for a genetic relationship between oil content and flowering time, grain filling period or single seed weight. The results indicate that for closely correlated traits conditional QTL mapping can be used to dissect the genetic interrelationship between two traits at the level of individual QTL. Furthermore, conditional QTL mapping can reveal additional QTL with small effects that are undetectable in unconditional mapping.

Identification of quantitative trait loci associated with oil content and development of near isogenic lines for stableqOC-A10inBrasscia napusL.

“…Furthermore, the mean values of both parental lines and RIL populations showed large difference between environments. Genetic analysis showed that the heritability of oil content in F 5:6 and F 6:7 populations was high (Table 1), which was consistent with previous studies (Zhao et al 2005(Zhao et al , 2006Delourme et al 2006;Wu et al 2006). These results suggested that seed oil content was mainly controlled by genetic factors as compared to environmental factors in these environments.…”

“…Recently, some studies have used parental lines with significant differences in oil content (>10%) (Sun et al 2012;Wang et al 2013), which was useful to detect QTL. These studies showed that QTL for oil content were distributed on 18 of 19 B. napus chromosomes, except chromosome C4 (Ecke et al 1995;Zhao et al 2005Zhao et al , 2006Zhao et al , 2008Zhao et al , 2012Delourme et al 2006;Qiu et al 2006;Sun et al 2012;Wang et al 2013;Jiang et al 2014). The number of QTL detected varied from three (Ecke et al 1995) to 27 (Chen et al 2010) and explained phenotypic variation ranging from 1.2% (Delourme et al 2006) to more than 20% (Chen et al 2010;Sun et al 2012).…”

“…Some efforts have been made in quantitative trait loci (QTL) mapping for oil content in rapeseed (Ecke et al 1995;Burns et al 2003;Zhao et al 2005Zhao et al , 2006Zhao et al , 2008Zhao et al , 2012Delourme et al 2006;Qiu et al 2006;Sun et al 2012;Wang et al 2013;Jiang et al 2014) that shed light on dissecting the genetic mechanism of oil content and provide a theoretical basis to develop effective breeding methods. Most of this research has been carried out using doubled haploid (DH) populations, including DY ('Darmor-bzh' × 'Yudal') and RNSL ('Rapid' × 'NSL96/25') (Delourme et al 2006), TN ('Tapidor' × 'Ningyou7') (Qiu et al 2006;Jiang et al 2014), SG ('Sollux' × 'Gaoyou') (Zhao et al 2005(Zhao et al , 2006(Zhao et al , 2008(Zhao et al , 2012, Z5 ('ZY036' × '51070') (Sun et al 2012), and KN ('KenC-8' × 'N53-2') populations. Meanwhile, only a few studies based on recombinant inbred line (RIL) population ) and intervarietal subsets of substitution lines (Burns et al 2003) have been performed.…”

Predictive Modeling of Biomass Component Tradeoffs in Brassica napus Developing Oilseeds Based on in Silico Manipulation of Storage Metabolism

“…Genotypespecific and environment-dependent negative correlations between percentage oil and percentage protein in rapeseed seed have been reported (Grami et al, 1977;Gunasekera et al, 2006;Peltonen-Sainio et al, 2011). Closely linked quantitative trait loci for oil and protein contents have been detected in rapeseed (Zhao et al, 2006). These findings demonstrate that a genotypeor environment-dependent tradeoff between the two components is highly relevant; therefore, TAG/protein storage might be manipulated if the underlying mechanisms of control and regulation are understood.…”

Conditional quantitative trait locus mapping of wheat seed protein-fraction in relation to starch content

“…This method was first applied to the studies on QTL of developmental behavior in rice (Cheng et al 2013), maize (Osman et al 2013), cotton (Ye et al 2003), soybean (Jiang et al 2010;Han et al 2011), wheat Zhu et al 2011;Jiang et al 2013). Several studies on the analysis of multiple related traits in conditional QTL mapping methods (Zhao et al 2006;Wang et al 2012), defining the genetic relationship among different traits at the QTL level.…”