Continued self-pollination results in :

Continued self-pollination result in inbreeding depression. This usually reduces fertility and even productivity.

The progeny of crosses between different varieties of a plant species usually exhibit greater biomass and fertility than either parent. This  phenomenon, called heterosis or hybrid vigour, is capitalized on to produce superior yields for many crop species.

Occurrence of more than one embryo in a seed is referred to as polyembryony.

Variations in gene frequency that occurs by chance rather than natural selection is known as genetic drift.