| Yield is influenced by genotype,environment and genotype×environment?G×E?interaction.G×E interaction is an important factor in the breeding process.In this study,using North Carolina Design?,sixteen inbred lines were test-crossed with two testers including Zheng58 and Chang7-2,thirty-two crosses were generated.This experiment was conducted at 3 locations in Shaanxi province for 4 consecutive years?2014-2017?to identify the combining ability of inbred lines under the conditions of three densities(45000,67 500 and 90 000 hm-2).The objectives of this research were to:1)determine genotype?G?and genotype-by-environment?G×E?interaction variation for grain yield;2)invetigate the variation of yield under different densities,different locations and different years;3)evaluate the relationship among the environments?location-year combination?using the GGE bioplot;4)determine the general combining ability effect of inbred lines and the highest mean performance and absolute stability of hybrid combinations under different densities.The main results are as follows:1.With the density increasing,the overall average yield of the hybrid combination increased significantly,and the yield at each location also increased significantly.The medium density increased by 6.2%compared to the low density overall average yield,and the high density increased by 11.2%compared to the low density overall average yield.It shows that increasing density is still an important measure to increase the yield of maize hybrids.2.The results of combine analysis of variance show that there were significant differences among the sources of variation in yield traits under different density conditions.With the increase of density,the mean squares of genotype?G?,location?L?,genotype×year?G×Y?and genotype×location×year?G×L×Y?were gradually increased.Under different density conditions,the environmental effects?L+Y+L×Y?accounted for 66.94%,60.71%,and 54.38%of the total sum of square?G+E+G×E?,respectively;Genotype variation accounted for 20.41%,21.17%,and 26.20%of the total sum of squares,respectively;The variation between genotype and environment?G×L+G×Y+G×L×Y?accounted for 8.90%,13.21%,and 12.94%of the total sum of square,respectively;It indicates that the environment effects is the most important cause of yield difference,and the variation caused by genotype is greater than the interaction between genotype and environment.Combining ability analysis of variance showed that the general combining ability?GCA?and special combining ability?SCA?mean squares were significant for grain yield under different densities.Mean squares for GCA were larger than SCA across environments,indicating that additive gene action was more important in the inheritance of grain yield.3.The results of combining ability showed that the four inbred lines of K12TC,KB081,KA105 and KB106 had higher GCA and stable performance under the three density conditions.4.The high yield and stability analysis of hybrid combinations showed that the number of hybrid combinations with high yield and stability increased with increasing density.Under the three kinds of density conditions,the combination of Zheng 58×K12TC,Zheng 58×KB106,Chang 7-2×91227,Zheng 58×KB081,Zheng 58×PX04,Chang7-2×KA105 has better yield and stability.5.Using the GGE bioplot,the correlation analysis between 12 environments?location-year combination?showed that all the test environments were on the right side of the GGE bioplot?the angle is less than 90°?,and the overall correlation was greater.Under three densities,the vectors of Yangling and Changwu locations were always in the first quadrant of the GGE bioplot.The environmental vector angle between the two locations was small,indicating that the Yangling and Changwu locations are highly correlated.The possible reasons are the pressure of two environments are similar,both are adversity environments,so the vector angle between the two locations are small.At high density,the environment vectors of the two locations are intertwined,indicating that the environmental pressures are more similar.The vectors of Yulin location is always in the fourth quadrant,and the correlation with Yangling and Changwu is relatively small.The possible reason is that the environmental pressure of Yulin is small. |
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