Analysis Of Cold Resistance And Identification Of SCoT Molecular Markers For Caladium Bicolor EMS Mutant Materials

Caladium bicolor is a perennial foliage plant in Araceae.It has colorful leaves and a special leaf shape,heart-shaped,resembling the ear;With the different varieties,the leaf color also has rich change,which leads to important ornamental value and a wide market prospect.Caladium bicolor originated from the tropical regions of South America with the optimum growth temperature of 25-30°C and poor cold resistance.To some extent,it has limited the application and promotion of Caladium bicolor in a northern border region like Chongqing.Undoubtedly,Breeding Caladium bicolor varieties with improved cold resistance,which is an effective way to solve this problem.In this experiment,morphological observations,physiological indicators and DNA molecular markers were used to identify and screen EMS-induced Caladium bicolor mutants,in order to establish the technology system of screening and identificating cold-resistant variant strains of Caladium bicolor.The main findings of this study are as follows:1.The obtained mutagenic materials were observed in the field for two periods of growth.It was found that some plants had relatively obvious changes in appearance,such as leaf color,leaf shape,and red ratio.Based on the characteristics of field morphological changes,these phenotypic variants are classified into 7 categories.At the late stage of the first growth cycle,under low temperatures,it was found that the dates of the downed seedlings of the two phenotypic variation categories were significantly delayed.It is presumed that the two types of phenotypic variation plants have strong cold resistance.2.Based on modified CTAB method,through single factor and orthogonal design,a suitable SCoT-PCR reaction system was established.The concentration of each component was as follows:10×buffer 2ul;DNA template 80ng;Mg²⁺concentration1.5mmol/L;and primer concentration 0.7μmol/L;Taq DNA polymerase 1.25U;dNTPs concentration 0.5mmol/L;and the optimal number of cycles was 35 times.On this basis,the optimum annealing temperature for the screened primers was discussed.The results indicated that the optimized reaction system was very stable.3.The system was used to detect the stable phenotypic variants observed,4 phenotypic variants were detected at the molecular level and were designated as S₁,S₂,S₃,and S₄.Compared with the control,the differences of the mutant strains in SCoT-PCR amplification were missing,new,missing and new.4.The SCoT PCR amplify 10 samples,a total of 93 bands were obtained,of which72（77.4%）were polymorphic.From the UPGMA,the coefficiet of genetic similarity of the 10 Caladium bicolor ranged from 0.60 to 0.84.The materials were divided intotwo groups at a genetic similarity coefficient threshold of 0.60.The genetic similarity coefficient between the S₁,S₂,S₃,and S₄ mutants and WT was 0.785,0.710,0.720,and0.645,respectively.The results showed that the genetic variation of the four mutants changed at the molecular level.5.Under low temperature,SOD activity,POD activity and proline content of S₁ and S₂mutants were significantly higher than WT.MDA content was significantly decreased,and the relative electrical conductivity was smaller than WT,indicating that the mutant strain was more resistant to cold than WT.