Trade-off between gene diversity and seedling production for gene conservation: Cornus kousa as a model

Theory on the trade-off between gene diversity (status number) and seedling utilization was applied into Korean Cornus kousa populations. Constraints on seedling utilization among families could be made on the parental proportion as both low and upper bounds. The low bound (minimum contribution) means that seedlings are not used from families with very low contribution. The upper bound (maximum contribution; contribution limit) describes balancing, meaning that the equal numbers of seedlings are utilized from families with high seedling production to avoid over-representation of the most fertile. For gene conservation of C. kousa, a total of 40 families were collected from natural distribution areas and propagated to produce 505 individuals (on average 12.6 trees per family). As a case of the ex situ gene conservation of C. kousa, the status number was estimated to 20.3 if all seedlings were used. Higher status numbers could be obtained by balancing the number of seedlings utilized per family. But, this high status number was connected to loss of seedling utilization. If it was decided to truncate the progeny size at 32 trees (lower bound = 0.0, upper bound = 0.8) where the contribution of each family was restricted as less than 6.0%, this increased the status number from 20.3 to 22.6 while 87.0% of seedling was used. In conclusion, a trade-off between equalizing parental contribution and obtaining an acceptable amount of seedling was achieved by controlling parental contribution, based on a power function [F(x) = xa], and gene diversity during the initial phase of mobilizing for the natural gene pool of C. kousa could be monitored.