The study looked at how durum wheat in Morocco has improved over time in terms of grain yield. Researchers used a method called path coefficient analysis to understand how different factors contribute to yield. They found that newer varieties of wheat have higher yields because they have longer growing periods and heavier grains. The study also showed that grain yield is influenced by three main components in both old and modern varieties. Overall, there has been a genetic gain of 23 kg per hectare in grain yield from older to newer varieties.