Abstract: 24 quality protein maize (QPM) inbreds were crossed with 4 temperate normal elite maize inbreds, which represents 4 major heterotic groups in China, by NCⅡ mating design in the study. The 96 crosses were evaluated in three different environments in Yunnan province for grain yield. The objective of this study was to determine combining ability between quality protein maize inbreds and temperate normal maize inbreds. The results indicated that a high yield general combining ability(GCA)of the inbred lines YML761, CML171, CML172, Zhongxi096/o2, YML411, YML024 and YML042 have been observed and these inbred lines will be predominant lines in maize breeding and commercial production in China. 24 Inbred lines were classified four heterotic group , i.e. Lancaster (YML411, YML042, CA307, YML065 and YML401), Ludahonggu(CML165, CML166, YML761, Zhongxi096/o2, Chang631/o2, YML011 and YML872), Tangsipingtou(CML171, CML161, CML172, Qi205, CA10139, YML330, 8129) and Reid (CML163, CML170, H152, Chang709/o2 and YML024).

Key words: Quality protein maize, Inbreds, Combining ability, Genetic relationship