Microsatellite Paternity Analysis Used for Evaluation of Outcrossing Rate Among Five Hevea Rubber Clones in a Systematic Seed Orchard

Abstract

A first generation of synthetic rubber (Hevea brasiliensis) clones derived from a polycross among multiple parents was produced to establish a seed orchard that will be useful to systematically enhance cross-pollination among several clones and breed superior rubber genotypes. The objective of this study was to evaluate the flowering patterns and outcrossing rate among five Hevea rubber clones within this seed orchard using microsatellite markers. Five rubber clones (AVROS 2037, BPM 1, IAN 873, PB 260 and RRII 118) were systematically grown in a random design with spacing of 7 × 7 m in a seed orchard at the Phetchabun Highland Agricultural Development and Research Center, KhaoKho, Phetchabun (16°35” N and 100°57” E), Thailand. Five pairs of polymorphic microsatellite primers were used to analyze 288 seedlings derived from the seed orchard. The five microsatellite loci chosen for this study were highly polymorphic, with a mean of 5.8 alleles per locus and a combined exclusion probability of 0.988553, both of which were sufficiently high to correctly assign parentage. Individual female parents varied in their estimated outcrossing rate from 58.62 to 98.36%, while the overall outcrossing rate in the seed orchard was 79% and selfing rate was 21%. Pollen contamination was not observed in this seed orchard. The high outcrossing level and the lack of pollen contamination may be useful for the establishment of a seed production facility and for the management of hybrid production.