Methods to Overcome Incompatibility

It has been possible to facilitate the germination of incompatible pollen by extracting pollen wall proteins from compatible pollen and supplying these during interspecific crosses. The pellicle, which lies over the cutinised wall of the stigmatic papillae is functionally important in the capture and hydration of pollen grains and may also be the site of the recognition reactions. Within Oenothera stylar grafting experiments led to pollen tube growth in incompatible styles. Treatment with Ca⁺⁺ resulted in pollen tube growth in incompatible style to some extent in Oenothera. Emasculation of immature flowers in Petunia reduced pistil elongation and weakened the incompatibility barrier. In general relatively high temperature has been found to inactivate the incompatibility mechanism and the site of activation has been the style.

Self-incompatibility in Lilium could be overcome by an interaction of temperature and 1% solution of naphthaleneacetamide-in lanolin. Heating of intact and detached style in water at 50? for 6 min before pollination could also overcome incompatibility. The stigmas of some plants with sporophytic incompatibility have a cuticular layer which serves as an incompatibility barrier. Pollen of such plants possess a cutinase enzyme system for destroying the cuticular layer.