| Maize is a major grain crop in Sichuan Province and also an important feed crop and a cash crop suitable for the deep processing into various products. Its sown area is 1.25 million hectares for an average year in the whole province, with a total production of 6.2 million tons. Over last 20 years, the maize production in Sichuan has developed substantially and its total production has got three consecutive leaps. However, as a big province in pig production and brewery, Sichuan still has a very sharp contradiction between the demand and the supply of the maize and imports a large quantity of maize from other provinces every year. It is an issue of very great concern for maize breeders and agro-technical management personnel in Sichuan Province how to further improve maize breeding level based on the existing breeding capability in order to ensure a sustainable and steady increase of maize production in Sichuan in the 21st century. The purpose of this research is to summarize the work of maize breeding which once made a great contribution to maize production in Sichuan Province, to analyze in a scientific way the causes of its achievements and subsequently to discuss the countermeasures and main direction of attack for maize development in Sichuan Province in the 21st century.Data in hybrid maize regional trails in Sichuan Province from 1981 to 2000, and analyzes the agronomic traits, quality characters and changes of disease resistance of hybrid maize varieties included in the regional trails over last 20 years are collected. 30 inbreds, which are obtained from a combination of each year's first two in mountain group and plain and hilly group of hybrid maize regional trails in Sichuan Province from 1981 to 2000, are used as materials to conduct a complete diallel cross trial of main inbred lines. Based on 30 inbred lines mentioned above, by adding 48-2A, HUANG ZAO SI, DAN 340 and 18-599- Red and removing four inbred lines QI 205, 286-4, NAN21-3 and 156, the SSR analysis has been conducted on 30 main maize inbred lines in Sichuan Province. The main results are as follows:1. During last 20 years, the production of hybrid maize in regional trails inSichuan Province have been increased year by year, with the largest margin during the Ninth Five-Year Period over the Eighth Five-Year Period, and mountain group greater than plain and hilly group. The increased production in plain and hilly group mainly results from the increased number of ear-lines and the increased production in mountain group comes from joint efforts of the weight of 1000 kernel, the number of ear-lines and the number of line-kernel, with the weight of 1000 kernels playing a major role.2. Over last 20 years, the maize hybrids bred in the early 1990s have relatively more resistance germplasms on bipolaris Maydis than on northern corn leaf blight and maize head smut Those bred in the middle and late 1990s have more resistance germplasms on northern corn leaf blight and maize head smut and the majority of them have quite good resistance against these three major diseases. In general, the level of disease-resistant maize breeding in Sichuan Province is improving continuously.3. In last 20 years, the maize hybrids bred in Sichuan Province has no dramatic changes in grain size and quality character. Their protein and starch contents have no obvious change and only the fat contents have a slight increase as the breeding years shift.4. Compared with inbred lines bred in 1980s, Sichuan's inbred lines bred in 1990s have no major changes in respect of growth and development period, ear length, the number of line-kernel and have a slight decrease in the height of plant and the number of ear-lines, however, have a tendency of increase in die weight of 1000 kernels. The results of diallel cross analysis show that both general combining abilityand specific combining ability reached an extremely significant level among materials on trial. There exists diversity of combining ability among 30 inbred lines and the difference of genera...
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