| Pre-harvest sprouting(PHS)is an important problem in wheat production worldwide.PHS in wheat causes terrible loss in grain quality and yield,particularly in regions with prolonged wet weather during the harvest season.As a quantitative trait,PHS is influenced jointly by genetic and environmental factors.At present,PHS resistance genes in wheat have not been well characterized at the nucleotide sequence level.Additionly,the numbers of genes with rich allelic variations are not enough to meet the needs of improvement of PHS resistance in wheat breeding.Therefore,identification of superior alleles for improving PHS resistance and development of functional marker will contribute to develop wheat varieties with high PHS tolerance.Mother of FT and TFL1(MFT),belongs to phosphatidyl ethanolamine binding protein(PEBP)family,has recently been shown to inhibit seed germination in wheat.PTF1 was a transcription factor with a bHLH domain,which was proved to relate with PHS in maize;however,its homologus genes have not been reported on wheat.In this study,we detected novel variations inTaMFT-3A,developed functional markers for PHS resistance in Chinese micro-core collections of wheat,and validated effects of the novel alleles on PHS resistance using linkage and association analysis.Based on the results,wheat varieties pyramiding favorable alleles of TaMFT-3A were selected for PHS resistance breeding.Simultenously,the association of TaPTF1-B1 allelic variations with PHS resistance was analyzed through gene-specific marker.The regulation mechanisims of TaPTF1-B1 on PHS resistance was also discussed in this study.The main findings of this study are as follows:1.An InDel variation(33 bp)in the-194 of the promoter of TaMFT-3A was detected between Chinese white-grained wheat varieties Annong0711(PHS tolerant)and Henong825(PHS susceptible),and developed a gene-specific marker(TaMFT-A2).Linkage analysis indicated that the TaMFT-A2 co-segregated with a major QTL(designed Qphs.ahau-3A)controlling PHS resistance on 3AS in the population from the cross of Annong0711×Henong825,explaining 13.85-16.12% of phenotypic variations.Associationanalysis showed that the TaMFT-A2 was significantly associated with PHS resistance in262 wheat varieties and 275 Chinese mini-core collections of wheat,suggesting that it can be used for marker-assistant selection of PHS resistance breeding.2.Four mutations in TaMFT-3A,including SNP-222,SNP646,SNP666 and TaMFT-A2,were evaluated the association with PHS.Multiple comparison analysis indicated that varieties carried favorable alleles SNP-222 had averages GI and FS of 0.30 and 0.14,which were significant lower thanthe materials with other mutations across different environments(P < 0.01).Several white-grained varieties pyramiding four favorable alleles of TaMFT-3A,which hadsignificantly lower GI and FS values,could be used for improvement of PHS tolerance in wheat breeding.3.TaPTF1-Bl contained two allelic varieties,which were designated as TaPTF1-B1 a and TaPTF1-B1 b.GI and FS values of wheat varieties carrying TaPTF1-B1 a were significantly higher than that of wheat varieties carrying TaPTF1-B1b(P < 0.01).TaPTF1-B1 b was considered as a superior allele for PHS resistance in wheat.With the breeding process,the distribution frequency of TaPTF1-B1 b is getting lower and lower,which is negatively chosen..In the Jing411×Hongmangchun21 RIL population,a major QTL for seed dormancy on 7B was detected at 5 and 15 days after harvest,explaining 8.39%-11.46% of phenotypic variations.4.In different imbibition of dormant and non-dormant Hongmangchun21 seed,the TaPTF1 gene expression is consistent with the changes of the ratio of ABA/GA,and contrary to the expression of the TaGA20 ox and TaGA3ox2,key genes in GA synthesis pathway.We speculate that the TaPTF1 gene positively controls seed germination through participation in GA and ABA synthesis pathway,however its details still needs to be further verified. |
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