Analysis Of QTL Mapping For Shank Length Of Three RIL Populations In Maize

The shank of maize is a small stem developing from stem node,connecting ear and stem.It is the only channel transporting photosynthate to the ear.On the one hand,shank length is significant negatively correlated with dry matter contents of kernel,negatively correlated with yield traits.On the other hand,there is a close relationship between it and the tightness of husk leaves,so the dehydration rate is affected by shank length.And it is related to the efficiency of mechanical harvesting.Therefore,controlling shank length within a suitable range will benefit for improving yield,grain dehydration and mechanical harvest.However,there is no any research about the QTLs and key genes of shank length regulated,and we have no ideal of the genetic basis of it.Hence,in this study,we measured the shank length at the harvest stage of 3recombinant inbred lines(RIL)populations,BY815/DE3,BY815/K22 and CI7/K22 which had been genotyped.We analyzed the correlations between shank length and husk traits,detected shank length associated QTLs,predicted of the candidate genes.These results are the basis of fine-mapping,provide available molecular markers for improving shank length in breeding,and contribute to clarify the genetic mechanism the development of shank length.The major results are as followings:1.Although,extensive variation of shank length and transgressive segregation were discovered,it was a mid-parent trait as a whole in the 3 RIL populations.The phenotypic value of shank length was changed continuously,and showed a slight leftward normal distribution.The significant correlations between phenotypic values in different environments,suggest the shank length in RILs is relatively stable in different environments.And genotypic differences were the main components of the total variation.Moderate levels of heritability were observed for the 3 population.Therefore,shank length is a quantitative trait and regulated by genetic factors in the 3 population.QTL linkage analysis of shank length can be performed.2.The significant positive correlations between shank length and husk length,husk number and the negative correlations between shank length and husk width.And these correlations suggest thatshank length and husk traits are regulated in the same developmental pathways.In addition,high significant positive correlation was discovered between husk length and husk width,which indicates that the length and width of husk may keep consistent in growth and development.3.In the BY815/DE3 population,we identified 4,5,6 and 5 QTLs which were mainly located on chromosomes 1,2 and 8,in 3 environments and BLUP value,and the contribution rate was between 4.8%and 17.52% for each QTL.There were 2,2,5,and 5 QTLs identified in 3 environments and BLUP value,mainly located on chromosomes 2,4,and 6,and the range of phenotypic variation contribution rate of each QTL was 4.2%-20.2%.And in the CI7/K223 population,the number of associated QTLs in the 3environments and BLUP value was 4,3,3,and 5 respectively,they were mainly distributed on chromosome 2 and 9,and the range of phenotypic variation of contribution rate was 5%-13.4%.There were6 major QTLs which identified in different single environments or BLUP value among all QTL,and these major QTLs with environmental stability could be fine-mapping.Moreover,there were 4 specific QTLs in the BY815/DE3 population,2 in the BY815/K22 population,and 3 in the CI7/K22 population,and 2 overlaps between BY815/K22 and CI7/K22 in the 13 major QTLs among the 3 populations.It suggests that the genetic background play an important part in identifying QTLs and some conserved genetic regulatory intervals control shank length among different populations.4.The range of physical distance of top bin is 0.08-19.25 Mb.And 263 gene were found in the total top bins,from which 14 candidate genes were identified.These candidate genes belong to two functional types,4 genes are the structural protein gene involved in the growth and development,the other 10 genes encode production involved in regulating the metabolic processes of plants.