Embryonic genetic load for a neotropical conifer, Pinus patula Schiede et Deppe

Genetic loads tend to be higher for widely distributed boreal and temperate pines compared to other plants and most animals. Although genetic loads ha ve not been estimated for neotropical pines, it seems likely that genetic l oads will be lower due to disjunct population structure and high rates of e ndemism, Embryonic genetic load is reported for a founder population of Pin us patula, a neotropical species used as a Zimbabwe exotic. The study was b ased on a novel orthogonal inbred mating design with 5 grandparents and 12 parents equally represented at four levels of inbreeding. Contrary to predi ctions, P. patula had an average of six to eight embryonic lethal equivalen ts, a genetic load comparable to temperate and boreal pines, Embryo viabili ty declined linearly with increased inbreeding levels (F = 0-0.5), supporti ng the independent lethal model. P. petula appears to have a stable embryo- lethal system despite small population sizes.