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2. Genetic determinism of complex traits


2.1. Effect of linkage on the variation of quantitative traits. QTL fine mapping

Using advanced intermated populations has been proposed as a way to increase the accuracy of mapping experiments. An F3 population of 300 lines and an advanced intermated F3 population of 322 lines, both derived from the same parental maize inbred lines were jointly evaluated for agronomical traits. We observed that:

  • The genetic variance for grain yield is significantly lower in the intermated F3 population, which suggests that single QTL in the classical F3 population should generally correspond to clusters of QTL in coupling phase  (Huang et al., 2009, Genetics)
  • This hypothesis was validated by the fine mapping of one QTL that showed that its apparent pleiotropic effect for grain yield and quality was due to two different QTLs with small effects.

2.2. Multiparental QTL mapping designs and allelic series

We contributed to the development of the BioMercator software to carry out meta-analysis of QTLs (in collaboration with the ABI team of the lab, Sosnowski et al., 2011, Bioinformatics, available at

http://moulon.inra.fr/index.php/fr/equipestransversales/atelier-de-bioinformatique/projects/projets/135). We used this software to reduce the confidence intervals of QTLs for silage quality (Truntzler et al., 2011, Theor Appl Genet) and water drought tolerance traits (Welcker et al., 2011, Plant Physiol). To get further insight into the allelic diversity of QTLs, we performed QTL detection in connected-multiparental designs, considering IBD probabilities of chromosome segments of parental lines  (Bardol et al., 2013, Theor Appl Genet).

 

2.3. Heterosis

We extended the North Carolina design III (NCIII) by using three populations of recombinant inbred lines derived from three parental lines belonging to different heterotic pools, crossed with each parental line to obtain nine families of hybrids. Most of the QTL detected for grain yield are located in pericentromeric regions and display apparent overdominance effects and limited differences between heterozygous genotypes, whereas for grain moisture predominance of additive effects was observed (Larièpe et al., 2012, Genetics).