| Heading date not only affects the seasonal and regional adaptability of wheat,but also is closely related to important agronomic traits such as high and stable yield of wheat.With the frequent occurrence of extreme weather,mining the genes related to heading date and exploring their regulation mechanism have become an urgent need to cultivate new wheat varieties that adapt to different environments.The CASL4AL(late maturity)in this study is a chromosome arm substitution line(CASL)in the background of Chinese spring(early maturity),whose long arm of chromosome 4A is replaced by the corresponding chromosome of the wild emmer TTD140.Previous laboratory studies have located the heading daterelated QTL at 616-617 Mb of wheat chromosome 4A using this substitution line.Follow-up studies have found that the heading date phenotype of CASL4 AL and its progeny line 257(CASL4AL and CS crossing and inbred progeny)under different light and temperature environments is very complex,which may be regulated by multiple loci.In order to explore the reasons,CASL4 AL and CS and their progenies F3 and F4 populations were used to locate the heading date-related genes by genome-wide resequencing,transcriptome sequencing,BSR-seq and map-based cloning techniques.Using CASL4 AL and CS and their extra early maturity and late maturity progenies for vernalization experiments,the difference of vernalization demand of different materials was used to explore whether the heading date-related genes were photoperiod genes under the condition of meeting the vernalization demand.The results are as follows:1.The results of whole-genome resequencing and transcriptome sequencing of CASL4 AL showed that the homozygous SNPs were not only enriched in 40-745 Mb of the Chr4 A,but also existed in high density on non-replacement arms such as Chr2 B,Chr5B and Chr7 B,and clustered on the non-replacement arms such as Chr1 A,Chr2A,Chr2 D and Chr5 D.Most of the non-replacement arm SNP enrichment regions are wild emmer wheat fragments,and a small part are DNA mutation,which indicates that there may be heading date-related genes on the non-replacement arm that affect the heading date of CASL4 AL.2.With the analyze of transcriptome sequencing data by AF and QTLseqr method,three heading date-related QTLs were located on 44-84 Mb of 2B chromosome and 518 Mb and 597-665 Mb of 4A chromosome,respectively.3.On the basis of the rough mapping mentioned above,336 and 337((CASL4AL × CS)F2)inbred progenies F3 were used as fine mapping population.two QTL with phenotypic variation explanation(PVE)of 11.49 %,LOD value of 5.07 % and PVE of 24.71 %,LOD value of 10.49 % were located at 638 Mb and 691-692 Mb of chromosome 4A,respectively.A major QTL with PVE of 73.57 % and LOD value of 47.85 was located in the 49-55 Mb of chromosome 2B.Therefore,the heading date of CASL4 AL is mainly controlled by the genes on chromosomes 4A and 2B,among which the gene related to the heading date on 2B chromosome is the major gene.4.According to the location interval,89 materials with four different genotypic combinations at 4A and 2B loci were selected from(CASL4AL × CS)F3 population.5.The results of vernalization experiment of wheat at different heading stages showed that vernalization had quantitative accumulation response and threshold response.The quantitative accumulation response is that when the vernalization time is less than 20 days,the heading date of wheat is significantly shortened with the increase of vernalization time,and the threshold response is that when the vernalization time is more than 20 days but not more than 30 days,the variation of wheat heading date obviously weakens or has no change.The vernalization demand of different materials was different,the vernalization demand of CASL4 AL was higher than that of CS,the vernalization demand of the crossing progenies of CASL4 AL and CS(extra early maturity and extra late maturity types)was between that of two parents. |
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