Inbreeding depression and biased paternity after mixed-pollination in Vaccinium myrtillus L. (Ericaceae)

We conducted a greenhouse study on Vaccinium myrtillus (a perennial species with a mixed mating system) to compare the fertility parameters following self-, cross-, and mixed-pollinations. Using an isozyme polymorphism, we also determined the proportion of selfed offspring in progenies obtained after mixed-pollinations. A high level of early inbreeding depression was observed (delta = 0.67), and a bias in the genetic representation of self and outcross markers in progenies from mixed-pollinations was detected. Offspring from mixed-pollinations were sired mainly (84.1%) by cross- pollen. The proportion of selfed offspring was correlated with the inbreeding depression estimates. However, those proportions were higher than the proportions expected on the basis of the individual inbreeding depression estimates. This might be explained by selective abortion of selfed embryos rather than prezygotic selection against self- pollen tubes.