This page explains about breed improvement.
You think that Japanese people are greatly partcular about rice, dont't you?
Breed improvement is improving quality of rice to develop better rice.
In short, it's "to make a new breed from another breeds".
Researchers are developing breeds which have the following properties.
・Easy to grow
This is how to breed improvement.
Most breed improvement take about ten years.
Moreover, if breed improvement reach the step: examinations to admit a new breed, in many cases, the research is canceled because demerits of the breed are found.