The Application Of Hydroponic Cutting Propagation Of Four New Varieties Of Platanus × Acerifolia And Flowering Related Genes In Germplasm Improvement

Platanus×acerifolia has a fast growth rate,a straight and tall trunk,and a broad crown,making it highly valuable for garden applications.However,the scattered pollen and seed hairs in spring and summer have been bothering people for a long time.In order to solve one of the problems,the research team has breeding for many years to obtain new late flowering and few fruits varieties such as‘Huanong Yunlong’,‘Huanong Ruifeng’,‘Huanong Lifeng’,and‘Huanong Qinglong’.In order to quickly promote these excellent varieties,to reveal the mechanism of its late flowering effect,this article conducts research from two aspects:hydroponic softwood cutting and its flowering related genes.The results are as follows:1.Establishment of a hydroponic softwood cutting system for‘Huanong Yunlong’.Conducting a three factor,two level L₄（2³）mixed level orthogonal experiment with hormone type,branch position,and leaf area.The results showed that hormone type had a significant impact on the number of rooting branches,different parts of branches had a significant impact on the number of days of initial rooting,while leaf area had a very significant impact on the rooting rate and number of days of initial rooting.The analysis results between different treatment combinations showed that the optimal combination for hydroponic softwood cutting of‘Huanong Yunlong’was that the area of leaves left in the cuttings was 1/3 of the original leaves.After being treated with 1000 mg/L KIBA+IBA hormone for 5 seconds,the rooting rate of the lower branches reached 83.3%,with 48.9 rooting numbers,the longest root length of 9.0 cm,the average root length of 4.2 cm,and the initial rooting days of 18.1 days.2.Establishment of a hydroponic softwood cutting system for‘Huanong Qinglong’,‘Huanong Lifeng’,‘Huanong Ruifeng’and the control‘Shandong Susheng’.Selecting‘Huanong Qinglong’,‘Huanong Lifeng’,‘Huanong Ruifeng’,as well as the commonly used variety‘Shandong Susheng’in the market for L₈（4×2⁴）based on five factors:genotype,solution type,hormone type,hormone treatment time,and leaf area mixed level orthogonal experiment.The results showed that genotype had a significant impact on rooting number,longest root length,and average root length.Solution type had a very significant impact on rooting rate,rooting number,and other four indicators.Leaf area only had a significant impact on rooting number.The varieties arranged in descending order of rooting rate are‘Shandong Susheng’,‘Huanong Lifeng’,‘Huanong Ruifeng’,and‘Huanong Qinglong’.The optimal combination of‘Shandong Susheng’treatment is to leave a leaf area of 1/2 of the original area and IBA treatment for 5 seconds is placed in tap water for hydroponics,and the rooting rate can reach 96.7%;The better treatment for‘Huanong Lifeng’is to leave 1/3 of the original leaf area and treat it with KIBA+IBA for 5 seconds in tap water for hydroponics,with a rooting rate of 90%;‘Huanong Ruifeng’has a leaf area of 1/2 of the original,treated with IBA for 5 seconds and placed in tap water for hydroponic cultivation,with a rooting rate of 70%;The best hydroponic effect of‘Huanong Qinglong’was achieved by treating it with KIBA+IBA for 7 seconds with a leaf area of 1/2 of the original,and placing it in tap water,with a rooting rate of 36.7%.3.By analyzing the transcriptome database of new varieties of late flowering and few fruit of P.acerifolia and combining with genome data,the flowering related genes Pa GIs,Pa FKF1s,Pa FTLs were cloned and named Pa GI1,Pa GI2,Pa FKF1a,Pa FKF1b,Pa FTL3,Pa FTL4,respectively.Through phylogenetic tree analysis and amino acid comparison analysis,it was found that these three types of gene sequence are highly conserved;Through q RT PCR,it was found that Pa GIs,Pa FKF1s,and Pa FTL3 among these three types of genes were expressed in the roots,stems,leaves,fruits,as well as various parts of the 2-leaf and 6-leaf stages of P.acerifolia.Pa FTL4was mainly expressed in the roots of different stages;Then,their expression patterns were analyzed in the annual leaves,subpetiolar bud,and flower buds of P.acerifolia.The results showed that these three types of genes may be involved in the regulation of flower development and dormancy in P.acerifolia.But the expression level of Pa FTL4 was extremely low and no obvious pattern was found;Pa GI1,Pa GI2,Pa FKF1a,Pa FKF1b,Pa FTL3 were further analyzed for their regulation modes under diurnal variation and low temperature short day environment.The results showed that they all had circadian rhythm,and might respond to low temperature short day environmental changes through different mechanisms;After heterologous transformation of these three types of genes into Nicotiana benthamiana,it was found that there were differences in plant height,leaf fruit size,flowering time,and other traits between the overexpression lines and the control.