The researchers studied different maize plants to see which ones would make the best hybrids for growing in Rwanda. They tested 45 different crosses in different environments and found that some plants had better grain yield when combined with others. They discovered that some plants had genes that worked well together, leading to higher yields. They also identified specific groups of plants that worked best together, which could help improve maize production in Rwanda and other similar regions. The study showed that a combination of different genetic effects could be used to create better maize plants for farming.