Analysis of a factorial mating design for the detection of relationships between quantitative traits and RAPD markers in larch

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Prat, D. | Arcade, A. | Faivre-Rampant, Patricia | Le Guerroué, Bénédicte | Pâques, L.E.

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* INRA, Centre de Recherche d'Orléans, URD, Ardon 45160 Olivet (FRA) Diffusion du document : INRA, Centre de Recherche d'Orléans, URD, Ardon 45160 Olivet (FRA). International audience. A factorial mating design involving European and Japanese larches was carried out in order to produce interspecific hybrids for afforestation in low-elevation stands in France. Hybrid families have been established in a single-tree-plot trial in Massif Central in France (elevation 540 m). Quantitative traits including growth characters, morphological characters and wood quality have been measured for 11 years. Parent trees were genetically assessed using RAPD markers. Ninety-eight markers showing intraspecific polymorphism in one species at least were used in this study. Firstly, family frequencies for a marker were deduced from parental frequencies for this marker, and statistical relationships between marker frequency and performance of the family were investigated. Relationships were significant for 19 combinations of markers and quantitative characters including height, branch angle, stem straightness and wood specific gravity. These markers are statistically linked to QTLs involved in these traits. Secondly, correlations between hybrid family performances and genetic distance of respective parents were investigated. A positive correlation between genetic distance and growth characters (height, volume, B.H. girth) and a negative correlation between genetic distance and branch angle were observed, and demonstrated the effect of heterozygosity level on these characters. Thus, genetic distance between parents is a first selection criteria if hybrid growth is, a requested characteristic. For a better knowledge of QTL-marker relationships, we are constructing a genetic map using a F1 interspecific family included in our factorial mating design. One map is expected for each parental species. Parents involved in our factorial mating design will be genotyped with molecular markers representative of the genome according to the genetic map. Additional QTLs will be assessed by analyzing on the one hand relationships between genotype and performance of progenies in several related families, and on the other hand relationships between parent genotype and family performance. Linkage disequilibrium will be evaluated in natural stands. This study deals with the possible application of marker-assisted selection in larch.

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