| Grain filling rate and grain filling duration are major determinants of grain yield.Understanding the contribution of grain filling related traits to the formation of kernel weight,revealing the changes in grain filling related and the growth period related traits for different eras of single-cross hybrids,identifying quantitative trait loci(QTL)for grain filling rate and duration to dissect the genetic basis of grain filling are significant to the theory and practice of breeding for improving maize germplasm and selecting elite hybrids with high yield.A set of 50 hybrids representing single-cross maize hybrids that were widely used in China from 1964 to 2014 were selected to study the changes in grain filling related and growth period related traits.Further,a recombinant inbred line(RIL)population including 172 families were developed from the cross between Huangzaosi(HZS)and Lv28 which are foundation parents used in maize breeding to identify QTL for grain filling rate and grain filling duration.The main results were as follows: 1.Changes in grain filling related and growth period related traitsFirstly,correlation analysis showed that grain filling related and growth period related traits reached a significant positive correlation with HKW expected for grain filling rate and duration in the lag phase and DS.Regression analysis showed that grain filling rate and duration in the effective grain filling phase could explain 54.46% and 43.40% of the phenotypic variation of HKW,respectively.The effective grain filling phase played a major role in the formation of HKW.Secondly,simple linear regression was used to against hybrid released year to analyze the changes in HKW,growth period related and grain filling related traits in four shared environments.The hybrids showed decadal change of 1.83 g·100-kernel-1 in HKW.With the change in HKW,DS increased firstly and then decreased,achieving the maximum value at 1980 s.AFPD presented an increasing trend and the rate reached fastest level between 1990 s and 2000 s.DPM increased firstly and then reduced at the 2010 s.In the part of grain filling related traits,W2 and W3 showed decadal changes of 1.23 g·100-kernel-1,0.64 g·100-kernel-1.T2 and T3 showed decadal changes of 18.14 ℃day,22.43 ℃day.However,there was no significant difference in grain filling rate of different phases.Therefore,the increasing of the grain filling duration in the effective grain filling phase and the maturation drying phase maize yield will be helpful for maize yield incresing.Finally,12 Chinese hybrids and 15 U.S.hybrids were widely grown in China released after 2000 were used to find the differences in the growth period related and grain filling related traits.In spring location,Chinese hybrids showed a longer period of DS and T1 than that of U.S.hybrids,while T2 and T3 of U.S.hybrids were longer than Chinese hybrids which played an important role in the formation of kernel weight.The Chinese hybrids and U.S.hybrids showed similar yields,while the U.S.hybrids went into the grain filling period early which was useful for grain dehydration.2.Genetic dissection of grain filling related and growth period related traits based on a high-density mapA total of 29 QTL were detected for grain filling related traits and 14 QTL were detected for growth period related traits under the single environment,which were distributed on the chromosomes 1,2,3,4,5,6,8,9 and 10.The LOD values ranged from 3.27 to 9.05,and the range of phenotypic variation explained were from 5.97% to 21.16%.Under the joint environments,QTL controlling the grain filling related traits were located at the same or similar positions of chromosomes and formed some QTL clustering regions on bin 1.05,bin 2.03,bin 4.05,bin 4.06,bin 7.04 and bin 9.04.Importantly,some QTL for grain filling rate in different grain filling phase were clustered on the region of 48.24 c M-135.72 c M on chromosome 4 and the region of 110.10 c M-114.73 c M on chromosome 9 that would be major regions for future grain filling research. |
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