The breeding system of the alpine shrubRhododendron ferrugineumwas studied at two sites of a population (site L and site H) in the French Alps. The aims were to estimate the degree of selling and (or) outcrossing and to determine if floral traits (including floral morphology, pollen to ovule ratio, stigma receptivity) may be related to the breeding system of the shrub. First, floral traits (corolla length and anther, and style heights) were measured, the number of pollen tetrads and ovules were counted, and the date of stigma receptivity and anther dehiscence were recorded. Second, five pollinations treatments (unmanipulated flowers, natural selfing, hand selfing, natural outcrossing, and hand outcrossing) were performed on 35 randomly chosen individuals in each site, and after each treatment the number of seeds per fruit was recorded. The results demonstrate thatRhododendron ferrugineumis self-compatible (self-compatibility indexensp;=ensp;0.95 and 0.97; auto-fertility indexensp;=ensp;0.92 and 0.98; selfing rateensp;=ensp;0.24 and 0.11 at sites L and H, respectively). Indices values are not significantly different between the two sites and facultatively xenogamous (pollen to ovule ratioensp;=ensp;669.5ensp;plusmn;ensp;280.5 and 845.2ensp;plusmn;ensp;246.9 at sites L and H, respectively).Key words: breeding system,Rhododendron ferrugineum, floral morphology, phenology, P:O ratio.
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