Identifying The Allelic Variations And Developing The Functional Markers In TaCKOX For Chlorophyll Content Of Flag Leaf And Grain Weight

Cytokinin (CTK) is an important hormone involving in the process of plant growth,by promoting cell division and expansion, breaking seed dormancy, stimulating buddifferentiation and delaing leaf senescence. As an one of key CTK metabolic enzyme, thecytokinin oxidase (CKX) has been proved to carry an important function in regulatingthe endogenous level of CTK in plant. In this research, the relationship between allelicvariation of CKX of wheat（Triticum aestivum L.） and the chlorophyll content of flagleaf, grain weight and grain density were investigated using a RIL population developedfrom the cross of Jing411and Hongmangchun21. And the results are as the follows.1.The chlorophyll content of the flag leaf of Jing411was higher thanHongmangchun21during the developing stages form heading to maturation.Thechlorophyll content of each line of RILs population showed a rising trend from headingto flowering and most of the lines, the content reached their highest level during theperiod from the late stage of flowering to early stage of grain filling stage, and thenbegan to decline. the chlorophyll content decreased faster at the late stage of grainfilling when the flag leaf started to yellowing.2.Based on the analysis, a tight relationship beween chlorophyll content of flag leafand grain weight at the stages from wheat heading date to grain filling, which had asignificant positive correlation. Especially at the stage of heading date, there was a bestcorrelation between them. At the stage of19days after flowering, the chlorophyll contenthad a weak relationship with grain because the flag leaf of most lines started to yellowing.In this study, the correlation was not sigficant between the chlorophyll content of fromthe heading time to maturation and grain density, which implied the main effect ofchlorophyll on grain weight of wheat.3.The four CKX genes, in this study, were screened by their good polymorphisms inthe RIL population, which were named Tacx6a02Tackx4, Tackx2a and Tackx3respectively. The analysis indicated that the allelic variation of Tackx4and Tackx3geneshad a close association with the chlorophyll content of flag leaf from the developingstages from heading to14after flowering which the correlations were all significant.However at the stage of19days after flowering, the correlation was not significant. Byanalyzing the differences in chlorophyll content of lines carrying A and B type allele ofthe Tackx3and Tackx4, the results showed that the lines with A allele had distinctly higher content of chlorophyll than the lines with B-type allele. These results couldconfirm that Tackx4and Tackx3genes are involved in the regulation of chlorophyllcontent of flag leaf from the stages of heading to early grain filling.4.As for the four CKX genes (Tacx6a02, Tackx4, Tackx2a, Tackx3), a closerelationship was obtained between their variations and grain weight. The grain weight ofthe lines carrying A-type was higher than that of lines with B-type allele. But the allelicvariation of these four CKX genes had a weak association with the grain in our research.These results implied that the four CKX genes had an important effect on the formationof grain weight.