Inducement And Comparison Of Cold Tolerance In Polyploid Betula Platyphylla

The study of polyploid Betula platyphylla has been an important direction in Betula platyphylla breeding.Due to the overall doubling of the plant genome,it has a significant increase in metabolite content,thereby enhancing the stress resistance and ecological adaptability of plants.At present,there are still some problems to be solved in the acquisition of plant polyploids.As far as Betula platyphylla is concerned,there are problems such as low induction rate of Betula platyphylla tetraploid and insufficient germplasm resources caused by single induction method of Betula platyphylla triploid.In view of the above problems,this study used Betula platyphylla as the material to optimize the tetraploid induction system,and carried out the study of high temperature induced female gamete chromosome doubling to create triploid,and discussed the growth and cold tolerance characteristics of polyploid Betula platyphylla.The findings are as follows :(1)Induction of allotetraploid of Betula platyphylla.Betula platyphylla seeds were used as materials,and the orthogonal test design of three factors and three levels was used to induce the tetraploid of Betula platyphylla by different colchicine concentration,different treatment time and different treatment temperature.The results showed that the induction rate of this method was between 1.33% and 6.67%.When the colchicine concentration was 0.3%,the induction rate could reach 6.67% at 30 ℃ for 3 d.(2)Induction of autotetraploid of Betula platyphylla.The sterile leaves of Betula platyphylla were used as materials to induce tetraploid of Betula platyphylla by tissue culture technology using two herbicides and colchicine.The results showed that the best induction time of the two herbicides was 2 d.When the concentration of amisulpride was 30 mg/L,the induction rate was up to 25.26%.When the concentration of pendimethalin was 15 mg/L,the induction rate was up to 20.45%.Colchicine is the best inducer of tetraploid Betula platyphylla.When the concentration of colchicine is 0.1%,pre-cultured for 2 d and induced for 8 d,the induction rate is as high as 74.81%.(3)The growth characteristics and cold tolerance of tetraploid and diploid of Betula platyphylla were analyzed.The results showed that the days of fast-growing period and the growth of fast-growing period of tetraploid were lower than those of diploid,but the leaf area,photosynthetic pigment content,photosynthetic rate and stomatal conductance of tetraploid were higher than those of diploid,and tetraploid had certain cold tolerance compared with diploid.(4)Creation of Betula platyphylla triploid and comparison of seedling growth characteristics.The female gametes of Betula platyphylla were induced by high temperature at different stages after pollination.The results showed that high temperature induced chromosome doubling of female gametes of Betula platyphylla could create triploids of Betula platyphylla.At around the 15 d after pollination,the female gametes were treated in situ at 40 ℃ for 1 h.The highest induction rate was 16.13%,and the highest induction rate was 7.14%at 42 ℃ for 1h at 21 d after pollination.The growth characteristics of Betula platyphylla triploid seedlings were higher than those of Betula platyphylla diploid except tree height,ground diameter,stomatal opening and leaf area.In conclusion,this study optimized the existing tetraploid induction system and explored the method of autotetraploid induction of Betula platyphylla,which improved the induction rate of Betula platyphylla tetraploid.A new method of triploid induction was created by heating the female gametes of birch at high temperature,which enriched the germplasm resources of Betula platyphylla triploid.