Study On Pear Mutation Induced With ⁶⁰Co-γ Radiation And Colchicine

In this study,⁶⁰Co-γ rays and colchicine were used to explore their mutagenic effects on pear.The dormant branches of ’Cuiguan’ and ’Yuluxiang’ pears were used as test materials,and different doses of ⁶⁰Co-γ rays were used for irradiation treatment to explore their mutagenic effects.Different concentrations of colchicine were used as mutagens to treat the ’Dangshan suli’ seeds and ’Pyrus ussuriensis’ callus,and their effect on polyploid induction was investigated.The main results are as follows:1.Biological Damage Effect of ⁶⁰Co-y Radiation on Pear BranchesThe annual dormant branches of ’Cuiguan’ and ’Yuluxiang’ pears were irradiated with 20,30,40,50（GY）and 4 kinds of ⁶⁰Co-γ radiation doses respectively and then were grafted.The survival rate of scions and mutagenic effects of leaves and branches were counted.At the same time,pathogenic bacteria of susceptible leaves of newborn leaves of irradiated branches were isolated and identified.The results showed that the survival rate of pear branches decreased with the increase of ⁶⁰Co-γ radiation dose,and deformity of leaves and the number of binary and trigeminal branches increased.The SPAD values of leaves germinated after radiation mutagenesis were analyzed by PCA and PLSS-DA.It was found that all radiation had obvious effects on ’Cuiguan’ pear,only two radiations（20,40（GY））had effects on ’Yuluxiang’ pear.2.Colchicine Induced Polyploidy of ’Dangshan’ Pear SeedsThe seeds of mature ’Dangshan suli’ fruits were soaked in colchicine with concentrations of 0.1%,0.5%and 1%for 12h,24h and 48h respectively,with clear water soaking as control.After 10 days of treatment,the germination rates of control and treated seeds were counted.Plant height,true leaf number,leaf shape index,stomatal density,chlorophyll content and chromosome ploidy were measured 60 days later,and their induction rates were calculated.The results showed that colchicine treatment with concentration of 0.1%for 12h was the most suitable for seeds.The tetraploid induction rate reached 6%.Compared with the controls,the induced tetraploid plants have lower stomatal density,larger stomata,lower leaf shape index and higher chlorophyll content.3.Colchicine Induced Polyploid of Pear CallusColchicine was used as mutagen and added into tissue culture medium to induce’Pyrus ussuriensis’ callus.The results showed that the polyploid induction rate reached 5%under 0.5g/L of colchicine medium treatment for 20 days.The mortality rate of callus increased with rising colchicine concentration in mixed medium.After treatments,the callus-growing plants showed severe browning in the early stage of seedlings,and the plants grew slower than the control.In the early stage of mutagenesis,the leaf morphology of tetraploid plants showed varied degrees of variation.Compared with control plants,tetraploid plants have larger stomata and smaller leaf shape index.