Trends in grain quality of starch, protein, fat and lysine content for normal maize varieties in China since the 1960s

Background and objectives: In China, breeders overlook changes in grain quality traits of starch, protein, and fat content that occur concurrently in normal maize (Zea mays L.). Here, we collected data for 436 single-cross normal maize varieties released since the 1960s and 258 landraces from China's three main agroecological regions to investigate how grain quality traits have changed over time. Findings: Since the 1960s, crude starch content has increased and protein content has decreased in northern China, crude starch content has increased and fat content has decreased in southwestern China and the Yellow-Huai River Valley, and lysine content has increased in southwestern China only. In the 2010s, northern China and the Yellow-Huai River Valley had the highest crude starch content, southwestern China had the highest crude protein content, and northern China had the highest crude fat content. Conclusions: Breeding since the 1960s has significantly changed the composition of maize seeds in the three main maize growing regions of China. Significance and novelty: This study provides a worthy summary of the changes in grain quality traits of normal maize varieties in China in the last 50 years and insights into developing strategies for breeding grain quality.