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.