Background: Gender and fertility variation have an impact on mating dynamics in a population because they affect the gene exchange among parental members and the genetic composition of the resultant seed crops. Fertility is the proportional gametic contribution of parents to their progeny. An effective number of parents, derivative of effective population size, is the probability that two alleles randomly chosen from the gamete gene pool originated from the same parent. The effective number of parents is directly related to the fertility variation among parents, which should be monitored for manipulating gene diversity of seed crops. We formulated a fundamental equation of estimating the effective number of parents and applied it to a seed production population.
Results: Effective number of parents (Np) was derived from fertility variation (Ψ) considering covariance (correlation coefficient, r) between maternal and paternal fertility. The Ψ was calculated from the coefficient of variation in reproductive outputs and divided into female (ψf) and male (ψm) fertility variation in the population under study. The Np was estimated from the parental Ψ estimated by the fertility variation of maternal (ψf) and paternal (ψm) parents. The gene diversity of seed crops was monitored by Ψ and Np. in a 1.5 generation Pinus koraiensis seed orchard as a case of monoecious species. A large variation of female and male strobili production was observed among the studied 52 parents over four consecutive years, showing statistically significant differences across all studied years. Parental balance curve showed greater distortion in paternal than maternal parents. The Ψ ranged from 1.879 to 4.035 with greater ψm than ψf, and the Np varied from 14.8 to 36.8. When pooled, the relative effective number of parents was improved as 80.0% of the census number.
Conclusions: We recommend the use of fertility variation (i.e., CV, Ψ), Person's product-moment correlation (r), and effective number of parents (Np) as tools for gauging gene diversity of seed crops in production populations. For increasing Np and gene diversity, additional management options such as mixing seed-lots, equal cone harvest and application of supplemental-mass-pollination are recommended.
Keywords: Effective population size; Fertility variation; Flowering assessment; Korean pine; Parental balance; Reproductive success.