Heterosis (hybrid vigor) for inbreeding species (that is, species that
usually self-pollinate, such as rice and wheat) can offer 20% to over 50%
yield increases, and, for example, a 68% increase in yield has been
achieved in foxtail millet (32). Strategies for using heterosis more widely to
increase yields in inbreeding crops center on finding ways of reducing the
cost and increasing the efficiency of producing hybrid seed. These include
identifying new sources of male sterility for hybrid creation [such as
thermosensitive genic male sterility in rice (33)] and using GM approaches
to engineer sterility and restore fertility (such as the InVigor Canola from
Bayer CropScience)]. Another possible mechanism for producing hybrid
seed involves the use of apomixis, where plants produce seed without the
need for fertilization. This allows hybrid vigor to be fixed. Creating
apomictic crop plants may also be possible as we learn more about the
genes controlling this process.