Is Eucalyptus Cryptically Self-incompatible?
OBJECTIVE
The probability that seeds will be fertilized from self- versus cross-pollen depends strongly on whether plants have self-incompatibility systems, and how these systems influence the fate of pollen tubes.


METHODS
In this study of breeding systems in Eucalyptus urophylla and Eucalyptus grandis, epifluorescence microscopy was used to study pollen tube growth in styles following self- and cross-pollinations.


RESULTS
Pollen tubes from self-pollen took significantly longer than those from cross-pollen to grow to the base of the style in both E. urophylla (120 h vs. 96 h) and E. grandis (96 h vs. 72 h). In addition, both species exhibited reduced seed yields following self-pollination compared with cross-pollination.


CONCLUSIONS
The present observations suggest that, in addition to a late-acting self-incompatibility barrier, cryptic self-incompatibility could be a mechanism responsible for the preferential out-crossing system in these two eucalypt species.
Horsley
Tasmien N
TN
School of Biological and Conservation Sciences, University of KwaZulu-Natal, Scottsville, South Africa. tasmien.horsley@sappi.com
Johnson
Steven D
SD
D001947:Breeding; D005052:Eucalyptus / Q000166:cytology / Q000502:physiology*; D005298:Fertility / Q000502:physiology; D008856:Microscopy, Fluorescence; D053205:Pollen Tube / Q000166:cytology / Q000502:physiology; D054817:Pollination / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D012639:Seeds / Q000254:growth & development