Pollen dispersal and genetic structure in a cajuput (Melaleuca cajuputi subsp. cajuputi) seed orchard in Yogyakarta, Indonesia

Cajuput (Melaleuca cajuputi subsp. cajuputi) is cultivated widely in Indonesia for its medicinal foliar essential oil. Breeding programs of cajuput have established seed orchards for the provision of improved seed to support the establishment of large areas of plantations. Information on pollen dispersal and genetic structure in such seed orchards is important for enhancing the genetic quality of seed produced from these seed orchards. We analysed eight microsatellite loci in 160 established trees and 240 offspring of ten selected mother trees in a cajuput seed orchard in Yogyakarta, Indonesia. We investigated the genetic structure and inheritance, pollen dispersal patterns and rates of pollen contamination. The parent trees showed high genetic diversity (H-O = 0.480, H-E = 0.755), but approximately 5% of alleles were not inherited by the offspring. Pollen dispersal in the cajuput seed orchard was panmictic, with an average pollen donor number (N-ep) of 17 and an average pollen dispersal distance of 43 m. However, 11.6% of genotypes contained a mismatch, indicating pollen contamination from nearby unselected cajuput trees. Stimulating synchronous flowering in the orchard and providing suitable habitat for pollinating insects may help to optimise outcrossing and random pollination within the seed orchard and thereby to fully capture genetic diversity and reduce pollen contamination.

Automated summary

Cajuput trees are widely cultivated in Indonesia for their medicinal properties, with breeding programs focused on establishing seed orchards to improve genetic quality. The genetic structure, pollen dispersal patterns, and contamination rates in a seed orchard in Yogyakarta were investigated. The parent trees exhibited high genetic diversity, with some alleles not being inherited by offspring. Pollen dispersal was found to be panmictic with a high pollen donor number and distance, although there was evidence of contamination from nearby unselected trees. Promoting synchronous flowering and pollinator habitats may help optimize genetic diversity and reduce contamination.