| In this study,five elite inbred lines of Danhuang 02,Zheng 58,Chang 7-2,He 344,and K10 which used in temperate maize production areas of China were used as the mainly parents and 200 inbred lines from domestic and foreign blood relationships were prepared.Totally,1000 hybrid combinations were identified and the related agronomic traits were identified.Finally,50 excellent combinations were screened out.For these combinations,comprehensive trait identification and evaluation were carried out in Heilongjiang and Jilin provinces at the same time in order to select nice varieties which were suitable for planting in middle-maturing area of northeast China.By analyzing the main agronomic traits and combining ability of the tested inbred lines and cross combinations,the results are as follows:1.Investigation of major agronomic characters of inbred linesThe parental inbred lines have a relatively large difference in growth period,and some parents were pollening and silking earlier.They are early-maturing varieties and are suitable for planting in regions with insufficient effective accumulated temperature;some parents are belonged to late-maturing types and are suitable for regions with sufficient accumulated temperature in the year.The correlation analysis showed that there was a significant positive correlation between the corn lodging rate and ear height,and the correlation coefficient reached r=0.669**.The ratio of ear height/plant height in maize was more affected by the height of the ear than the plant height.Under natural environmental conditions,most parental inbred lines exhibited strong disease resistance to leaf spot disease.However,there were 20 samples of silky smut,which accounted for10% of all test materials,and should not be used when breeding resistant varieties.2.Investigation and analysis of main agronomic traits in hybrid combinationThere was a significant positive correlation between maize yield and leaf number,100-grain weight and ear position.There was a highly significant positive correlationbetween yield and plant height.Through GCA analysis of five mainly parents,Zheng 58 contributed much more for the yield,K10 for the grain water content,and Chang 7-2 for100-grain weight.Analysis of grain SCA revealed that the yield of SCA in 390 crosses was positive.3.Selection and Evaluation of Excellent Hybrid Combinations of Medium MaturityFrom the 1000 crossed combinations,50 medium-mature hybrid combinations suitable for planting in the main producing areas of spring maize in Northeast China were selected.At the same time,identification and evaluation were conducted in Fanjiatun of Jilin Province and Hulan District of Heilongjiang Province.The results showed that the agronomic traits of the 50 excellent crossed combinations were consistent at the two experimental sites.The overall performance is that the silking period is between July 11 and July 21 in Jilin Province,and between July 18 and July28 in Heilongjiang.The mature periods are from September 8 to September 15 in Jilin Province.Also,the mature periods are between September 14 and September 22 in Heilongjiang Province.The results indicated that these hybrid combinations can be used as middle-aged corn germplasm resources in Northeast China.Under natural conditions,50 excellent hybrid combinations showed strong resistance to head smut,ear rot,large leaf spot,leaf spot,and stem rot.The grey relational degree analysis showed that the weighted association degree and equal weighted association degree of the crossed combinations HD1616,FT16001,and HD1606 were not significantly different,indicating that the three hybrid combinations had greater potential for increasing yield and stable yield.Compared with Xianyu 335,crossed combinations HD1625,HD1634,HD1633,HD1616,FT16016,FT16001,FT16015,HD1606,HD1623,HD1631,HD1602,HD1613,HD1632,HD1629,HD1610,HD1620,FT16007,HD1614,FT16014,HD1622 are better which can be used as fine resources for breeding spring corn in the northeast. |
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