Patterns of hybrid seed production in adjacent seed orchards of Acacia auriculiformis and A. mangium in Vietnam

Key message Hybrid seed production in adjacent seed orchards of Acacia auriculiformis and Acacia mangium was influenced by (i) flowering times of the two species and (ii) the distances of parent trees from the inter-orchard boundary. Approximately 80% of hybridisation events were found within 60 m from the boundary. Context Understanding pollen dispersal has important implications for breeding and seed production of pure species and hybrid Acacia . Aims We examined patterns of hybrid production in adjacent clonal seed orchards of A. auriculiformis and A. mangium in Vietnam. Methods We assessed the frequency of hybrid offspring using four species-diagnostic SSR markers in seed collected from a total of 72 trees (75 seedlings per tree) at distances ranging from 4 to 144 m from the inter-orchard boundary. The number of hybrid was determined from SSR allele peak sizes in pooled sample (10 seedlings per pool, 540 pools). Calibrations were developed from pools with known proportions of pure-species and hybrid material. Results Hybrid frequency differed significantly among individual clones ( P