ESTIMATION OF POLLEN CONTAMINATION AND MATING SYSTEM IN PINUS MERKUSII SEEDLING SEED ORCHARD USING ALLOZYME MARKERS

Abstract

The amount of pollen contamination and mating system parameters in a Pinus merkusii seedling seed orchard in East Java were estimated using allozyme gene markers. By running starch gel electrophoresis of enzymes from the haploid megagametophyte side by side with the diploid embryo, the precise information on male and female gametic contribution to the seed produced in the seed orchard was identified. The estimation was based on the single-locus allelic frequency differences between seed orchard populations and an unimproved plantation of the species surrounding the orchard. The study revealed high level of pollen contamination (29.7 ± 18%) in the seed orchard. Excess homozygotes obtained from the orchard suggests that consanguineous matings have occurred. Multilocus outcrossing rates of the three blocks and four local stands ranged from 0.137 to 0.305, and single-locus outcrossing rates ranged from 0.102 to 0.244. The seed orchard design, wind direction during flowering period and flowering synchronisation could have contributed to the pollen contamination and inbreeding observed. Although pollen contamination and inbreeding may be a problem in this seed orchard, the seed may still be useful. Management considerations for such seed orchard to deal with these problems are discussed.