| Wheat(Triticum aestivum L.)is one of the most important staple food crops in China.Tainong 18 is a main popularized wheat variety in Shandong province.And now,it is the backbone parent for wheat breeding.In this study,hydroponic culture trial and field trial were used to identify and compare the differences of important morphological and physiological traits related to nitrogen absorption and utilization between Tainong 18 and Linmai 6 at seedling and adult stages.In addition,the Recombinant Inbred Lines(RILs)derived from a cross of“Tainong 18×Linmai 6”were used to detect QTLs for important nitrogen efficiency related traits in germination and field trials.Thus,we could analyze the genetic control characteristics.These could lay a foundation for further promotion and application in wheat breeding of Tainong 18.The results showed that:(1)There were significant differences in absorption and utilization characteristics of nitrogen between Tainong 18 and Linmai 6.Compared to Linmai 6,Tainong 18 has stronger adaptability to low nitrogen(LN)environment both at the seedling and adult stages,and able to obtain higher grain yield and nitrogen utilization efficiency in LN environment.The root lengths of Tainong 18 were 11.38%and 19.00%higher than Linmai 6 in normal nitrogen(CK)and LN treatments,respectively.The root dry weight of Limai 6 was 24.39%higher than Tainong 18.The nitrate nitrogen uptake rate of Tainong 18 was significant higher than Linmai6.The chlorophyll contents(SPAD)in the flag leaves of Tainong 18 were significantly higher than Linmai 6 both in CK and LN treatments at the heading stage,flowering stage and early grain filling stage.The root nitrogen use efficiency,shoot nitrogen use efficiency and total nitrogen use efficiency of Linmai 6 were 27.94%,16.16%and 18.99%higher than Tainong18 in CK treatment at seedling stage.The root nitrogen use efficiency,shoot nitrogen use efficiency and total nitrogen use efficiency of Tainong 18 were 19.33%,10.20%and 13.11%higher than Linmai 6 in LN treatment at seedling stage.In CK and LN treatments of adult stage,the grain nitrogen use efficiencys of Tainong 18 were 44.44%and 20.00%higher than Linmai 6,respectively;the straw nitrogen use efficiencys of Tainong 18 were 9.76%and23.64%lower than Linmai 6,respectively.(2)The research about germination and adult traits of RIL derived from a cross of“Tainong 18×Linmai 6”indicated that the biomass and nitrogen efficiency related traits showed a continuous distribution in the RIL population,and they are typical quantitative traits.The coefficient of variations(CVs)ranged from 8.06%to 21.53%in germination trial and from 7.80%to 38.03%in field trial.The generalized genetic rates(h_B~2)ranged from 35.12%to 94.09%in germination trial and from 45.83%to 88.46%in field trial.(3)Combined with the ultrahigh density genetic map of RIL population and identification results of nitrogen efficiency related phenotype traits,fourteen QTLs were detected for the biomass related traits of germination stage and 156 QTLs were detected for main agronomic traits and nitrogen efficiency related traits of adult stage in this study.A total of 10(6.41%)relatively high frequency QTLs(RHF-QTLs)for adult traits can be detected under different nitrogen treatments,which have strong environmental stability.The average contribution of PH.1-1D(CKE6 LNE6)on chromosome 1D was 13.26%.The average contribution of SN-3B(CKE6 LNE6)on chromosome 3B was 11.38%.The average contributions of GW.3-4B(CKE6 LNE6),GNC.2-4B(CKE6 LNE6),ANC.2-4B(CKE5 LNE6),GN.3-4B(CKE6 LNE6),PH.3-4B(CKE6 LNE6)on chromosome 4B were 13.59%,8.54%,9.67%,32.18%and 8.96%,respectively.(4)The cluster was defined as the co-location of QTLs for more than two traits and it may involve some important genes that can simultaneously control or influence different traits.Fourteen QTL clusters(C1-C14)were mapped on nine chromosomes:2A,4B,4D,5B,5D,6A,6B,7A and 7B in this study.Among them,C3,C4,C6,C8 and C10 are important QTL clusters.Cluster C3 on chromosome 4B included eight QTLs,three of which were RHF-QTLs.The average contribution of all QTLs in C3 was 11.63%.Cluster C4 on chromosome 4B included six QTLs.The average contribution of all QTLs in C4 was 21.22%.Cluster C6 on chromosome 4B included four QTLs,one of which was RHF-QTL.The average contribution of all QTLs in C6 was 21.09%.Cluster C8 on chromosome 5B included three QTLs,two of which were detected for germination traits and one of which was detected for adult trait.Cluster C10 on chromosome 6A included six QTLs,one of which was RHF-QTL.These QTL clusters were detected for several different traits simultaneously and may involve some important genes related to nitrogen efficiency.(5)In this study,thirty-six QTLs,five QTL clusters and five RHF-QTLs were detected for biomass and nitrogen efficiency related traits on the 4B-1 chromosome.We found three important QTL cluster locations that related to nitrogen and phosphorus efficiency simultaneously(D-981323-D-1113185,S-1040960-D-3940950,S-3941408-D-1138250)by comparing with the locations for phosphorus absorption and utilization of the same RIL population.These locations may contain important genes related to nutrient efficiency in wheat.4B chromosome is importance to explain the difference in nitrogen efficiency between Tainong 18 and Linmai 6.And it is the focus of future research. |
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