关键词: 玉米, 粗蛋白质含量, ., Crude protein content, Hierarchical c

Abstract: In field experiments，crude protein content (CPC)and yield of fifty maize varieties widely planted in the north of China since 1990s were studied. By exploring analysis and testing of normality for stalk CPC，gain CPC，and whole-plant CP yield (CPY)，each of which accorded with normal distribution N（5.48，0.532），N（9.42，0.792），and N（530.67，64.632），respectively. The ranges of stalk CPC were 4.38%-7.09%，grain CPC were 7.03%-11.00%，whole-plant CPY were 417.43-726.72 g/plant. The stalk CPC was not significantly correlated with grain CPC (P＞0.05). Through hierarchical cluster analysis for stalk CPC and grain CPC of the fifty maize varieties，the maize varieties could be classified into 3 types：high-grain CPC with low-stalk CPC type（HGLS），low- grain CPC with low-stalk CPC type（LGLS），and high-grain CPC with high-stalk CPC type（HGHS）. Currently, maize varieties in the north of China were short of HGHS type hybrids which was only 20 percent，it is suggested that breeding and selection for this type of maize should be strengthened.

Key words: Zea mays L., Crude protein content, Hierarchical cluster analysis