Identification And Genetics Analysis Of Multi-floret Wheat Mutants

Wheat（Triticum aestivum L.）is one of the most important food crops in the world.Increasing wheat production is one of the important ways to ensure world food security.The three factors of wheat yield are spike number per area,grain number per spike and thousand-grain weight,among which the grain number per spike is directly affected by the number of spikelets and florets per spike.Therefore,increasing the number of wheat florets is of great significance to improve the yield of wheat.Two multi-floret mutants were obtained by mutagenesis of hexa-ploid wheat Brundage by EMS.The two mutants were named bd-m2 and bd-m5 respectively.The wild-type Brundage could differentiate 3-6 florets per spikelet,the mutant bd-m2 could differentiate up to 25 florets per spikelet,and bd-m5 could differentiate up to 20 florets per spikelet.We identified the phenotype of the mutants,constructed a mapping population,and performed BSR-seq analysis.The main results are as follows:（1）Brundage could differentiate 3-6 florets per spikelet,the mutant bd-m2 could differentiate up to 25 florets per spikelet,and bd-m5 could differentiate up to 20 florets per spikelet.The statistics of florets per spikelet of wild-type Brundage,bd-m2 and bd-m5 showed that the num-ber of florets per spikelet of the two mutants was significantly higher than that of the wild-type,but most of the florets were sterile.According to the statistics of grain number per spike,spike-let number and spike length,it was found that bd-m5 was significantly higher than Brundage.The spike length,plant height and flag leaf wide of bd-m2 were significantly higher than those of Brundage,while bd-m2 and bd-m5 were significantly lower than Brundage in the statistics of stem internode length and flag leaf length.From the spikelet growth process of heading 0-35 days,it was found that the floret differentiation duration of bd-m2 and bd-m5 mutants was longer,indicating that the SM at the top of the spikelet of the mutants differentiated into FM for a longer time.The results of Alexander staining showed that the pollen viability of bd-m5was normal,and nearly half of bd-m2 was aborted.Due to the longer grain length,the 100-grain weight of bd-m2 mutant was significantly higher than that of wild-type and bd-m5 mutant.（2）When bd-m2 backcrossed with Brundage,the number of florets per spikelet in F₁ plant was not significantly different from that of wild-type.Phenotypic segregation appeared in BC₁F₂ generation,and wild-type phenotype:mutant phenotype=2.8:1（（?）~2=0.071,n=1）,which accorded with 3:1 segregation ratio.It was speculated that the multi-floret phenotype was a recessive trait controlled by a single gene.（3）There was no significant difference in the number of florets per spikelet in the F₁ gener-ation of the bd-m2 and AK58 hybrids compared with that of AK58.Phenotypic segregation appeared in F₂generation plants.（4）Select the leaves and spikelets of 25 individual plants of the“F₂-mut”and 23 individual plants of the“F₂-wt”,the leaves and spikelets of the BC₁F₂ extreme mutant phenotype,and the leaves and spikelets of the bd-m2 mutant to extract total RNA,performing RNA-Seq.The leaves of wild-type Brundage to extract genomic DNA for exon capture sequencing.The results of BSR-seq showed that the multi-floret gene of bd-m2 mutant was likely to be located on 5BL or 6BL chromosome.