| The seeds and branches of Populus×liaoningensis Z.Wang et H.D.Chen cv.nov Populus×gaixianesis Z.Wang et H.D.Chen sp.cv,Populus×deltoides cv.Lux ex. 1-69/55 and Populus×euramericana cv.San Martino ex.1-72/58 were respectively irradiated by 60Co-γwith 0 Gy,50 Gy,100 Gy,150 Gy,200 Gy,250 Gy and 0 Gy,10 Gy,30 Gy,50 Gy,70 Gy,100 Gy.The germination rates,growth situation and physiological characterics were investigated,as well as variance of their genome DNA were clarified by use of ISSR.Results are as follows:1.Germination rates of irradiated seeds and growth of their seedlings were investig germination rates and seedling height of the seeds indoor lower than control,but insignificant correlation were observed between it with irradiation doses.Roots growth of seedling significantly declined with the increase of radiation doses.As for poplar outdoor, germination rates,and growth of height and root-collar diameter of four cultivars decreased with the enhance of radiation doses.In terms of branches,survival rates and growth of height and root-collar diameter of the four cultivars treated with 10 Gy significantly higher than control.The survival rates declined sharply when the irradiation doses exceed 30 Gy,as well as decrease of growth of height and root-collar diameter.No living plant was observed when branches were treated with more than 50 Gy.2.For irradiated seeds,soluble protein content and CAT activities of leaves increased firstly,followed by decline with the enhance of irradiation doses.Whereas,the opposite change trend were observed in SOD activity and MDA content.The maxmum values of soluble protein contents,SOD activity and MDA content occurred under treatment of 50 Gy.while,CAT activity reached its maxmum value under 150 Gy.In terms of irradiated branches,soluble protein contents and SOD activity of leaves increased firstly,then declined with the enhance of irradiation doses,and reached its maxmum values under the treatment of 10 Gy.However,the opposite change trend happened in MDA contents,and the maxmum value occurred under 10 Gy.CAT activity has been an upward trend.The results indicated that high irradiation doses affected poplar resistance adversely.3.According to relative germination rates and relative survival rates,semi-lethal dose of seeds of P.×liaoningensis Z.Wang et H.D.Chen cv.nov,P.×deltoides cv.Lux ex.I-69/55 and P.×euramericana cv.San Martino ex.I-72/58 was determined on 200 Gy. While for P.×gaixianesis Z.Wang et H.D.Chen sp.cv was 150 Gy.As for branches, semi-lethal dose of P.×liaoningensis Z.Wang et H.D.Chen cv.nov,P.×deltoides cv. Lux ex.I-69/55,P.×euramericana cv.San Martino ex.I-72/58,and P.×gaixianesis Z.Wang et H.D.Chen sp.cv were respectively 10-30 Gy,10-30 Gy,30-40 Gy,10 Gy.4.The ploidy of the phenotype mutate plants were detected by use of flow cytometry, the results showed that all of them were diploid.5.ISSR amplification were performed in optimum reaction solution,including primers(2μm/L) 2.5μL,dNTPs(10 mmol/L) 0.5μL,MgCl2(25 mmol/L) 2μL,10×Reaction Buffer 2.5μL,Taq 1μL,DNA(20 ng/μL) 1μL,ddH2O 15.5μL.Modified thermal protocol consisted of all initial denaturation step at 94℃for 5 min,followed by 40 cycles of 94℃for 1 min,55℃for 45s and 72℃for 90s and a final extend to 72℃for 10 min.Amplification products were stored under 4℃untill analysized.Eight primers were selected out from 10 primers using criterion of polymorphism difference, and were adopted in the present study.6.ISSR analysis showed that,DNA polymorphism are different among the poplar with different irradiation doses.The irradiation doses groups had no significant laws in genetic similarity,and do not goes down with the radiation dose increases,but the genetic similarity coefficient in the plant with radiation dose is less than the control group. Between the species:The genotype similarity coefficient of the P.×liaoningen sis Z. Wang et H.D.Chen cv.nov between 63.9%-96.8%;The genotype similarity coefficient of P.×gaixianesis Z.Wang et H.D.Chen sp.cv between 58.6%-96.4%;The genotype similarity coefficient of P.×deltoides cv.Lux ex.I-69/55 between 65.3%-89.3%;The genotype similarity coefficient of P.×euramericana cv.San Martino ex.I-72/58 between 66.1%-94.9%.From the above we can see that P.×gaixianesis Z.Wang et H.D.Chen sp.cv is the most sensitive of radiation. |
