For qian, he claims that by changing plant environment such as done in 1950s such as more fertilizer, more plants per square foot field, one can increase the yield hundred times.

However, given a rice strain in modern agriculture (with sufficient fertilizer), the photosynthesis rate is fixed, and the yield is predictable. The key is genetics.

Yuan is correct in that he suggests better rice strain will have higher yield. He focuses on genetic issues although he has not done much about modern molecular genetics.