Estimation of effective pollen dispersal distance for cross-pollination in chestnut orchards by microsatellite-based paternity analyses

Abstract

Chestnut (Castanea spp.) is mainly self-sterile, so interplanting of different cultivars in orchards is recommended. However, effective pollen dispersal distances for cross-pollination in chestnut orchards have not been determined. We examined pollen dispersal in three chestnut fields by tracking the movement of cultivar-specific pollen through paternity analysis based on simple sequence repeat (SSR) markers. We genotyped 48 major cultivars with 20 SSRs and constructed a reference database, from which we inferred the pollen parent of each seed. In Field A, which consisted of a single row of pollinizer ‘Riheiguri’ and four rows of ‘Porotan’ at distances of 4, 8, 12, and 16 m from the pollinizer row, the percentage of seeds sired by the pollinizer pollen was higher at 4 and 8 m from the pollinizer trees (65.3% and 61.1%, respectively) than at 12 and 16 m (37.5% and 43.1%, respectively). The percentages of bur set and yield per tree decreased as the distance from the pollinizer row increased (66.2%, 42.4%, 33.7%, and 24.8%; 7.0, 2.5, 1.6, and 1.1 kg: 4, 8, 12, and 16 m, respectively). In analyses of two other fields, which contained interplanted rows of different cultivars, the percentages of seeds sired by pollen from cultivars planted in adjacent rows were much higher than from cultivars planted in more distant rows. These results suggest that it is important to plant different cultivars in adjacent rows.