Typically, a rice panicle contains only about a hundred grains, and even the largest panicle yields only a few hundred grains.
Why can crossing rice with barnyard grass yield a “thousand-grain panicle”?
Because barnyard grass is a wild plant, it grows roots quickly, has a robust body, and thrives vigorously. The wild nature of barnyard grass is not only evident in its roots and stems but also in its reproductive capacity. It can flower and produce seeds prolifically, spreading its progeny extensively. Its seeds are hardy, resistant to sun and flooding, and do not rot easily. Given the right environment, they germinate and grow rapidly. Although the ancestors of cultivated rice were also wild, thousands of years of cultivation have domesticated their growth and reproductive instincts, which are now much milder compared to barnyard grass. When they are crossed, the offspring inherit the traits of barnyard grass—fast rooting, vigorous growth, and especially prolific flowering and seed production, resulting in the development of the “thousand-grain panicle.”
Of course, crossing rice with barnyard grass is not a simple task. We want the progeny of the cross to remain rice and not revert to barnyard grass, but with enhanced flowering and seed production. Therefore, we use rice as the mother and barnyard grass as the father, allowing rice flowers to be pollinated by barnyard grass, which then develop and grow after fertilization.
The offspring from the rice and barnyard grass cross tend to have variable traits, so they must be provided with a good environment and carefully nurtured. This is necessary to gradually stabilize the characteristics of the “thousand-grain panicle” and to further improve its development.