Southern pollen sired more seeds than northern pollen in southern seed orchards established with northern clones of Pinus sylvestris

Abstract

Contamination by southern pollen is a considerable problem in Scots pine (Pinus sylvestris L.) seed orchards established with northern clones. This study investigated whether the contamination was due to the competitive superiority of southern pollen by carrying out competition trials using mixtures of pollen from northern and southern populations of Scots pine. Trials were performed in a southerly seed orchard established with clones originating from northern populations. Seed paternity (siring) was determined through the analysis of allozyme variation. Southern genotypes sired significantly more seeds (76%) than their northern competitors and across all mixed-pollen crosses. Maternal genotype had no effect on seed siring success. The mean flower abortion rate was lower in southern pure-pollen crosses and mixed-pollen crosses than in northern pure-pollen crosses. The results show that local pollen may induce high levels of background pollination in southern seed orchards composed of northern genotype grafts. These results must be taken into account when aiming to produce suitable reforestation material for northern areas.

Keywords:

• Background pollination
• competition crosses
• pollen competition
• pollen contamination
• seed siring success

Acknowledgements

We wish to thank Aulis Leppänen, who was in charge of the crossings, field measurements and seed handling. Annukka Korpijaakko was responsible for the laboratory work carried out in the Foundation for Forest Tree Breeding and Finnish Forest Research Institute.

Additional information

Notes on contributors

Leena Koivuranta∗

Present address: ∗Licentia Ltd, Helsinki, Finland

Annika Parantainen†

Present address: †Finnish Institute of Occupational Health, Turku, Finland