Fertility variability among clones and genetic diversity of seed crops at seed orchards of Chamaecyparis obtusa in South Korea

Chamaecyparis obtusa (Siebold & Zucc.) Endl., commonly known as Japanese cypress or hinoki cypress, is widely cultivated for its high-quality timber and ornamental use. Despite its economic and ecological importance, the species faces challenges in adapting to various climates, necessitating the distribution of high-quality seeds and seedlings. This study aims to enhance the genetic improvement and stability of seed production by analyzing fertility characteristics and genetic traits from two clonal seed orchards of C. obtusa in two locations (Gochang and Seogwipo), South Korea. We examined patterns of strobilus and cone production from 2020 to 2022, assessed effective parent numbers, genetic diversity, and heritability estimates, and analyzed parental contribution for the reproductive traits. Results indicated significant annual variation in strobilus and cone production among clones, with higher male fertility variance than female parents. The effective parent number and genetic diversity were generally maintained sustainably, though Seogwipo showed slightly lower diversity. The study underscores the need for management practices to balance clonal contributions, and sustain long-term productivity and genetic diversity in the seed orchards of C. obtusa. Future research should focus on understanding environmental influences on clonal contributions and refining selection criteria for superior clones in the advanced generation breeding program.