| Dragon fruit（Hylocereus spp.）belongs to the order of the triangular prism genus（Hylocereus）and the family of Cactaceae.It is native to central America,Colombia,and has been planted commercially in more than 20 countries.Dragon fruit is welcomed by domestic and foreign consumers due to its unique flavor and rich nutrition.In recent years,the dragon fruit industry in China has been developed rapidly but restricted.Because the variety of dragon fruit is single,especially the lower fruit setting rate and the smaller fruit led by the self-incompatibility of red dragon fruit（H.monacanthus）.The polyploid breeding has been considered as an important way to creat new varieties of fruit trees.In this paper,we used red dragon fruit as material,and delved further into the establishment of regeneration system of optimal culture conditions on the basis of previous studies,and then explored the optimal concentration of colchicine for chromosome doubling with best time in vivo and in vitro induction of polyploid,providing a theoretical basis and technical reference for rapid propagation and polyploid breeding study of red dragon fruit.The main research contents and results were as follows:（1）We used stems and cotyledons as materials,and designed single factor and two-factor plant growth regulators combination,adding different plant growth regulators,then screened the optimal stem callus induction and proliferation,cotyledon callus induction and proliferation,stem bud induction and proliferation,bud root culture medium formulation.The results showed that the optimal stem callus induction medium formulation was MS+2,4-D 2 mg·L-1+6-BA 4 mg·L-1,the rate of callus induced was38.52%,the optimal stem callus proliferation medium formulation was MS+6-BA 4mg·L-1+NAA 0.5 mg·L-1,the rate of callus proliferated was 45.19%.The optimal cotyledon callus induction medium formulation was 1/2MS+2,4-D 3 mg·L-1+6-BA 2mg·L-1,the rate of callus induced was 88.52%,the optimal cotyledon callus proliferation medium formulation was 1/2MS+6-BA 1.5 mg·L-1+NAA 3 mg·L-1,the rate of callus proliferated was 36.67%.The optimal stem bud induction medium formulation was MS+6-BA 3 mg·L-1+NAA 1 mg·L-1,the rate of bud induced was42.96%,the optimal stem bud proliferation medium formulation was MS+6-BA 3mg·L-1+NAA 1.5 mg·L-1,the rate of bud proliferated was 87.04%.The optimal bud root induction medium formulation was 1/2MS+NAA 1 mg·L-1,the rate of root induced was 95.19%.（2）We used seeds,seedlings,stems and cotyledons as materials,and designed different concentration of colchicine combined with different treatment time in vivo and in vitro induction methods of polyploid,then screened the optimal methods of inducing dragon fruit polyploid.The results showed that in vivo induction,the best combination of soaking seeds by different concentrations of colchicine combined with different time was 0.1%colchicine combined with 24h,the rate of variation was 64.72%,the rate of doubled or more was 12.67%.In vitro induction,the best combination of dripping stems by different concentrations of colchicine combined with different time was 0.05%colchicine combined with 21d,the rate of variation was 90.93%,the rate of doubled or more was 34.44%.The best combination of soaking stems by different concentrations of colchicine combined with different time was 0.01%colchicine combined with 24h,the rate of variation was 24.22%,the rate of doubled or more was 21.56%.The best combination of soaking seedlings by different concentrations of colchicine combined with different time was 0.2%colchicine combined with 12h,the rate of variation was21.94%,the rate of doubled or more was 3.33%.The best combination of mixed-culturing cotyledons by different concentrations of colchicine combined with different time was 0.1%colchicine combined with 14d,the rate of callus was 16.11%.Considering the time of colchicine treatment and the rate of doubled,the best effect on polyploid induction was soaking stems in vitro.（3）Compared with the contrasts,the variants grew slower and became shorter but thicker.The root length,width and height were 0.58,2.04 and 0.19 times of the contrasts respectively.The leaves of variants tended to be round and the relative chlorophyll content increased so the leaves were dark green.The leaf thickness,length,leaf index and the relative chlorophyll content were 1.49,0.40,0.45 and 1.27 times of the contrasts respectively.The stomas of variants became longer so the number of stoma of each field had lessened,thus the stomatal density became smaller.The stomatal length and stomatal density were 1.49 and 0.47 times of the contrasts respectively.The chromosome number of contrasts was 2n=22,the chromosome number of variants was4n=44 mixed with 22 or other numbers.In this study,the chromosome number of variants was changed but all the variants were chimeras.For H.monacanthus,the karyotype formulas of diploid cells and tetraploid cells were 2n=22,2sm+20m and4n=44,44m respectively.Conclusions:the regeneration system in vitro and induction method of polyploid for H.monacanthus were relatively obtained. |
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