The researchers studied how different genes affect the yield and characteristics of rice plants. They crossed different rice varieties to create new hybrids and observed traits like plant height, grain yield, and leaf area. They found that most traits were influenced by non-additive gene action, meaning the traits were not simply a combination of the parents' traits. Heterosis, or hybrid vigor, was mainly due to over-dominance of certain genes. This suggests that selecting for specific traits may be challenging as they are not easily fixed in the offspring. The study showed that combining different rice varieties had a significant impact on the expression of these traits, with non-additive gene effects playing a major role.