Protein quality and quantity of quality protein maize (QPM) and non-QPM hybrids under optimal and low nitrogen conditions

Background and objectives Quality protein maize (QPM) nutritional quality involves high total protein content but reduced zein accumulation in maize endosperm, leading to increased non-zein proteins, hence higher levels of essential amino acids such as lysine and tryptophan. The aim of this study was to assess the effect of low nitrogen (N) conditions in one location, and optimum conditions in three locations, on zein proteins in 10 QPM hybrids developed by the International Maize and Wheat Improvement Centre (CIMMYT) compared to two non-QPM checks. Findings With a few exceptions, total protein content, and gamma- and alpha-zein peak areas were significantly reduced under low N compared to optimal conditions, while beta-zein increased. Non-QPM hybrids had higher protein content than QPM hybrids, and QPM hybrids had higher gamma-zein than non-QPM in all environments. Higher alpha-zein values than other zein types were observed in non-QPM than in QPM genotypes in all environments. Significance and novelty Low N significantly reduced protein content and all the zein fractions except for beta-zeins, which were increased. The advantages of a decrease in zein fractions in QPM under low N conditions were offset by a large decrease in grain protein content.