Fertility variation, seed collection and gene diversity in natural stands of Taurus cedar (Cedrus libani)

Abstract

Seed stand is a natural forest population that is one of the essential seed sources for global seed supply. Individual fertility is an ability to produce progeny to next generation. Prediction of fertility variation is useful for seed quality, ecosystem management and gene conservation. Fertility variation and gene diversity in seed stands of Taurus cedar were estimated based on the difference in strobilus production between female and male parents. A total of 50 trees were randomly chosen from each stand, and female and male strobili were counted for three consecutive years. The mean of female strobili ranged from 31 to 150, and that of male ranged between 77 and 828. The variation in strobilus production was subjected to estimation of female and male fertility variation. The total fertility variation ($\Psi$) was estimated from the female and male fertility variation. The $\Psi$ in a good crop year was smaller than in a poor year. The effective number of parents (N_p) was calculated based on the $\Psi$, which varied from 34.7 to 44.2. When strobilus productions were pooled across 3 years or populations, the N_p increased. Equal cone harvest could mitigate the fertility variation among individuals but caused loss of seed production. Mixing seeds from different years could also decrease the fertility variation and increase the gene diversity of seeds. However, a balance between the size of N_p and the number of pooling years should be carefully considered for maintaining the gene diversity in the natural stands.