Autotetraploid Induction Of Forsythia Suspensa And Its Response To Cold And Drought Stresses

Forsythia suspensa is an important garden ornamental plant and a bulk medicinal crop.Although forsythia has a strong ability to tolerate cold and drought,seedlings are often damaged by low temperatures,and long-term drought stress will also affect their growth.In order to obtain new varieties with high stress resistance,this study used the seeds of forsythia as materials to induce the autotetraploids by soaking in different concentrations of colchicin.Diploids and artificially induced autotetraploids of forsythia were used to explore the mechanism of gene dosage balance after WGD of species and the effect of dosage effect on phenotype,cold and drought tolerance.The results are as follows:1.The results were found that the seeds were soaked in a mixed solution of 0.4%colchicine and 2% DMSO for 72 h,and the induction effect was the best,with an induction rate of 14.44%.2.The autotetraploids and diploids were compared by leaf length,leaf width,leaf area,leaf thickness,plant height,etc.The results showed that the plant height of autotetraploids were significantly lower than that of diploids,the leaf width and leaf area were significantly larger than diploids,the leaf leaves were thicker than diploids.There was no obvious difference between node spacing,leaf length,petiole length,and the leaf color of autotetraploids and diploids.3.By comparing the gene expression between autotetraploids and diploids under normal growth and cold stress,we found that only 0.56% to 1.35% of the effectively expressed genes had dosage effect,while most of the genes had no difference in expression.Our results showed that the forsythia autotetraploids took a "shock-type" method to keep the gene dosage balance after WGD,that is,most genes were inactivated and a few genes produced dosage effect.However,these few genes with dosage effect were mostly random,and we speculated that it was due to the increased interaction between chromosomes after WGD.4.According to the enrichment results of cold stress response genes in diploids and autotetraploids,the genes in "response to abscisic acid" and "cold acclimation" were considered the important factors that made autotetraploids have stronger cold adaptability.Especially,the gene expression in "cold acclimation" might reduce the influence of cold stress on other genes.5.Based on the phenotypic,biomass,and rapid chlorophyll fluorescence parameters of autotetraploids and diploids,it is concluded that autotetraploids has stronger drought adaptation.This study induced autotetraploids of forsythia,and revealed the mechanism of maintaining gene dose balance after artificial doubling by comparing diploids and autotetraploids.The comparison of phenotypes,biomass and chlorophyll fluorescence parameters between diploids and autotetraploids showed that autotetraploids had stronger tolerance to drought and cold.This study provided new germplasm resources for forsythia breeding.