The Establishment Of Schizachyrium Scoparium Regeneration System And The Study Of Octaploid Induction

Schizachyrium scoparium is a warm-season ornamental grass,native to North America.It is widely used in plant landscape configuration for its unique plant type and beautiful inflorescence.However,with the rapid development of the application of ornamental grasses,the problem of single variety of Schizachyrium scoparium has gradually emerged.There is still a big gap between China and European and American countries in the cultivation of new varieties of Schizachyrium scoparium,so the germplasm innovation of Schizachyrium scoparium is particularly important.In this study,Schizachyrium scoparium root tip is used as experimental material to make chromosome tablet,and clear chromosome division phase is selected for karyotype analysis.The young panicle of Schizachyrium scoparium is used as the experimental material,and the regeneration system of Schizachyrium scoparium is established by adding different kinds and concentrations of plant hormones to induce callus.The polyploid induction of callus is studied by colchicine treatment to provide new germplasm for the cultivation and development of new varieties of Schizachyrium scoparium;by measuring the photosynthetic characteristics and chlorophyll content of the two.And the new germplasm Schizachyrium scoparium is analyzed and evaluated.The main results of this study are as follows:(1)Karyotype analysis of root tip chromosome of Schizachyrium scoparium shows that Schizachyrium scoparium is tetraploid.The number of chromosomes is 40,Schizachyrium scoparium karyotype formula: 2n=4X=40=36m+4sm.(2)The experimental results of Schizachyrium scoparium regeneration system show that the optimal medium for inducing callus using young panicles is MS+2 mg/L2,4-D+1 mg/L 6-BA,and the induction rate is able to reach 100% after three weeks of culture.MS + 2 mg/L 2,4-D + 1 mg/L 6-BA+2g/L Proline is the best callus breeding medium with a proliferation coefficient of 3.2 after one month of proliferation and culture.And the optimal callus differentiation medium is MS+0.25 mg/L NAA+1 mg/L6-BA,1/2MS+0.1mg/L IBA is the best rooting medium.(3)Using different concentrations of colchicine and different treatment time to do two-factor completely random test,polyploid induction of callus Schizachyrium scoparium is carried out.Finally,it is deter mined that the concentration of colchicine is0.2%,and the polyploid induction rate is 26.7% under the dark condition of 25±1℃for 72 hours.The identification methods are flow cytometry,stomatal identification and chromosome counting.Among them,the results of flow cytometry shows that the nuclear DNA content of the octaploid material is twice that of the control group.By observing the number of chromosomes on chromosome sections,the doubling results is confirmed.There are 40 chromosomes in tetraploid Schizachyrium scoparium root tip and 80 in octoploid.In addition,the stomatal size and density of the two are also very different.In the same unit area,the number of stomata in the octoploid plants is less and the stomata are larger.(4)Compared with the tetraploid parents,the plant height of the plants after chromosome decreased by 69 cm,and the average number of headings per plant is reduced.With the same time,the phenological period is delayed 20-40 days.However,there is no significant difference in photosynthetic characteristics and chlorophyll content between octoploid plants and their parents.