Principles of Plant Breeding (2+1)

Pseudo-compatibility

• Incompatibility plants show some degree of self fertilization. This is known as pseudo compatibility. The avenues are used for creating homozygous S lines and maintain them by selfing. The following ways are used to maintain self incompatible species and strains by self-pollination.

a. Bud pollination:
It is supposed that some compound which inhibits the pollen germination and tube growth is produced by stigma and style at the time of flowering. If pollination is done 24 hours before the natural flower opening, there is compatibility. Probably the inhibitor compound is not produced by that time. This is known as bud-pollination and is widely used in maintaining lines in grapes, cabbage, cauliflower, etc.

b. End of season pollinations:
Usually when the crop season is about to end, incompatibility mechanisms weaken, This probably due to less metabolic activity of the plant and failure of the plant to produce enough inhibitory compounds.

c. Stigma removal:
Failure of pollen to germinate of tube growth occurs in cauliflower, cabbage and radish. In these the removal of stigma and then pollinations results in perfect seed set.

d. Grafting:
In Trefoilparense, grafting of vegetative parts, either within a single plant (homograft) or between different plants (heterografts), have also improved the level of compatibility as reported by Evans (1969). The reason is not known. Pollination can be done after grafting.
Making polyploidy of incompatible strains they may become compatible because the altered genic balance at the tetraploid, level. The method has been utilized in peach and potato.