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Selection assistee par marqueurs (sam) dans un dispositif multiparental connecte - application au maÏs et approche par simulations

Guylaine Blanc 
Abstract : Detection of quantitative trait loci (QTL) for agronomic traits has received considerable attention in plant genetics since the late 1980's with the advent of molecular markers. Many studies, especially theoretical studies, have shown using markers linked to QTL for selection (Marker- Assisted Selection, MAS) could help increasing the efficiency compared to conventional selection. In plant genetics, most of the QTL detection experiments are performed on populations coming from the cross of two pure inbred lines. Thus much effort has been spent on populations with a low genetic diversity, even if the probability to detect QTL increases with the number of parents involved in the population. In a multiallelic context, connected multiparental populations (i.e. coming from crosses sharing a common parent) are particularly interesting as connections allow one, for a given population size, to increase the accuracy of QTL position, to compare for each QTL different alleles and to test for epistatic interactions with the genetic background. For MAS, markers should be particularly interesting in such designs to select individuals carrying good alleles coming from different parents and to conduct crosses to combine these alleles. The objective of this study was to validate the interest of a MAS scheme in a connected multiparental design. Six F2 populations, with 150 individuals each, were obtained from a diallel cross between four unrelated maize inbreds. QTL detection was performed on this design of 900 individuals with MCQTL software allowing taking into account connections. We observed a gain of power and an increase of the accuracy of QTL positions for QTL detection on the multiparental connected design compared to a detection without taking into account connections or on individual populations. Using these results we performed three MAS cycles for two schemes following different objectives: (i) improving earliness for the first scheme and (ii) improving grain yield while keeping a constant grain moisture at harvest for the second. To follow the transmission of parental alleles at the QTL during selection generations, a program to calculate identity by descent probabilities adapted to our design was developed. Genetic progress experimental evaluation revealed a significant improvement for earliness of 3 days for the first scheme and of 3.2q for grain yield for the second scheme. We compared by simulations different selection schemes, using parameters of the experimentation (number and effects of QTL, h²
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  • HAL Id : pastel-00003478, version 1



Guylaine Blanc. Selection assistee par marqueurs (sam) dans un dispositif multiparental connecte - application au maÏs et approche par simulations. Sciences of the Universe [physics]. INAPG (AgroParisTech), 2006. English. ⟨NNT : 2006INAP0039⟩. ⟨pastel-00003478⟩



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