| As a crucial role in maize breeding and food production, Elite inbred lines not only directly crossed a lot of wildly spread hybrids, but also derived many widely spread valuable parent inbred lines. However, all the backbone of the parents that played an important role in the maize breeding was generally summaried after they were widely used which certainly lacks of systematic theoretical basic research. Maize elite inbred line is the combined result of combination, optimization and coordination of many excellent genes of traits, and closely related with breeding objectives and environmental factors of different ecological zones. Why and how are a large number of widely spread valuable inbred lines selected from elite lines? What is the main contribution of elite inbred lines to their offspring? This is very important to research and utilite elite inbred lines. In this paper, we mainly research the formation and evolution mechanism of key inbred lines on agronomic traits, yield, environmental adaptation, and other important traits.In this study,68 inbred lines that consist of four elite inbred lines (Huangzaosi, Mo 17,478, Dan340,) and their derivative lines are used as materials to analysis the major phenotypic characters of these lines by planting in different years and maize producing areas. Analysis of variance (ANOVA) was conducted to determine the effects of environment (here, i.e., combination of location and year), inbred line, and their interactions, on each phenotypic trait. Then, mean, coefficient of variability and coefficient of genetic variability of each trait were estimated across all environments, and mean, coefficient of variability of each cluster by location. Finally, statistically significant traits were analyzed using the principal component analysis (PCA). Three principal components were selected to draw matrix plot to show the relationships of these key inbred lines.The main results are as follows:1. All the elite inbred lines in our research were divided in 4 main heterotic groups (i. e. Sipingtou, Luda Red Cob, Reid and Lancaster), which corresponded to the cluster determined by their pedigree information.2. In this research Huangzaosi and its derivative lines have the following characteristics:short maturity, shorter plant height, more compact, thinner stems, more tassel branchs and litter kernel per row, whereas the yield per plant, tassel branch, ear length and 100-kernel weight of Huangzaosi and its derivative lines have greater genetic variation. And that the maturity can be stable inherited. Maturity, leaf number, ear diameter and plant height can be inherited from Huangzaosi to its derivatives, while other characters obviously changed due to participation in other germplasm and different breeding objectives.Mo 17 and its derivative lines have the following characteristics:high plant height, long ear, big kernel and litter row per ear. Ear length, tassel branch and 100-kernel weight can be inherited from Mo 17 to its derivatives, while other characters changed obviously in different derivatives.478 and its derivative lines have the following characteristics:upright-leaf plant pattern, short plant height and ear height, long maturity, short bald length, high 100-kernel weight and yield per plant, and thick ear. The main characters can be stably inherited from 478 to its derivative lines except Lov and cob diameter.D340 and its derivative lines have the following characteristics:fiatten-leaf plant pattern, big stem, little leaves, bad stay-green, many rows per ear, blad length, and little kernels per row. Ear diameter, ear length, blad length and cob diameter can be inherited from Dan340 to its derivatives stably, while other characters obviously changed due to the participation of other germplasm and different breeding objectives.3. In this research, the stability of number of kernel per row and total leaves of Huangzaosi and its derivatives was the worst in different environments. There were little difference about the characters of plant height, Lov, mutarity, rows per ear, number of kernels per row and ear diameter in different years, while the stability are better. Total leaves, tassel branch,100-kernel weight, cob diameter, blad length and yield per plant were less stable between years, indicating a greater environmental impact by the weather. The best suitable identification traits of Huangzaosi were kernel depth and total leaves in the southwest ecological zone, plant height and stem diameter in Shandong and other traits in northeast maize area.The stability of Lov and ear length was the worst between environments of Mo 17 and its derivatives. The stability of agronomic and yield traits became worse by participated lines Ji63 and B73 of Reid group into Mo 17. With more blood of Mo 17, the derivative lines'stability of the yield traits in different environment was better. The best suitable identification traits of Mo 17 were ear height, total leaves, mutarity, ear length, rows per ear and cob diameter in the northeast ecological zone, and other traits in Shandong. The stability of ear height, tassel branch, total leaves, number of row per ear, number of kernel per row and kernel depth of 478 and its derivatives were the worst between environments, while the stability of plant height, stem diameter and cob diameter were best. The derivative lines with the more blood of 478 the better stability of yield traits in different environment, wherea have more stable agronomic traits. The best suitable identification traits of 478 were Lov and ear diameter in southwest ecological zone, while the ear height, tassel branch, total leaves, blad length, 100-kernel weight and cob diameter were more suitable identification traits in the northeast ecological zone, and in Shandong ecological zone, the best traits were plant height, stem diameter, mutarity, ear length, number of row per ear, number of kernel per row, kernel depth and yield per plant.The stability of tassel branch, stem diameter, number of row per ear, ear diameter and cob diameter of Dan340 and its derivatives were the worst between environments whereas the number of kernel per row,100-kernel weight and yield per plant were the best stabilities. The derivative lines with the less blood of Zi330 the worse stability of yield traits in different environment, whereas more stability according to pedigree analysis. The best suitable identification trait of Dan340 was total leave in southwest ecological zone, while the Lov, blad length, number of row per ear, number of kernel per row, cob diameter, ear diameter and kernel depth in the northeast ecological zone, and plant height, ear height, stem diameter, tassel branch, mutarity, ear length, 100-kernel depth and yield per plant were more suitable for in Shandong ecological zone.4. In this research, Mutarity, leaf number, ear diameter and plant height of Huangzaosi can be stable inherity. Therefore, we can easily obtain an upright-leaf plant type, short mutarity and plant height with the use of Huangzaosi and its derivative lines to improve inbred lines. Small ear of inbred lines can be improved by stable inherited trait of big ear of Dan340, and we can achieve better results when Dan340 as the male parent while we doing is. Mo 17 and its derivatives can be used to improve ear length and kernel depth, wherea the improve effect were significantly higher when as the female parent than male parent.478 and its derivatives can be used to improve most characters of inbred lines.5. There should be some characteristics of inbred lines for the development of maize induction and cultivation system. First of all, more stability inherited traits which are contribution to yield per plant. Second, some traits of lines which were stability in different environment are important. Third, widely basis is very important as well. Fourth, clearly heterotic groups will be useful when we prouduce hybrids. Then, excellent quality characteristics are important to market demanding. Finally, ecological adaptability is very important. Therefore, breeding objectives were different for maize inbred lines breeding in different ecological environment.
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