The Induction And Identification Of Homologous Tetraploid Onoin Plant

Onion(Allium cepa L.)attributes to the family of biennial liliaceous and allium herbaceous plant,which is a typical cross-pollination crop.Conventional breeding methods requires long breeding cycle,large workload while lacks efficiency.Comparatively,polyploid breeding can rapidly improve the quality,resistance and yield of onion.The establishment of onion high frequent vitro regeneration system lays a solid foundation for the onions polyploid induction in vitro.Vitro induction method has also been used for other allium plants.In this experiment we conduct the vitro induction of onion tetrapliod plants on the basis of high frequent vitro regeneration system,colchicines injected in onion living buds and seed soaked in colchicines.We adopt the most commonly used methods of polyploidy induction to explore the best method of inducing tetraploid onion so as to further shorten the breeding period,to improve the efficiency of breeding and to provide theoretical basis and technical guidance for innovating new onion germplasm.Diploid onion variety ’W433’ was used as the experimental material.Under the condition of vitro,we used dormant bulbs as explant to inoculate into the solid and liquid BDS mediums with different concentrations of colchicines.Using morphological identification,stomata size comparison and root tablet chromosome measurement,chromosomal polyploidy was identified,the morphological identification as well as the chromosome number identification demonstrated that both vitro and vivo induction were effective in inducing tetraploid somatic cells(2n=4x=32),among which solid BDS medium induction results showed that the prime tetraploid induction effect was to treat 0.02%colchicine for 24 h because there were 8 plants identified as tetraploid onions surviving from 300 treated onions;liquid BDS medium induction results showed that the prime tetraploid induction effect was to treat 0.01%colchicine for 24 h and 36 h tetraploid because there were 11 and 16 plants identified as tetraploid onions surviving from 300 treated onions.Overall speaking,liquid BDS medium induction effect is superior to solid BDS medium.However,the liquid medium treatment has weaknesses such as callus vitrification,higher infection rate and mortality.Different concentrations of colchicine were injected into the onion buds with different numbers to induce onion pollen variation so as to create tetraploid germplasm resources;Seeds were soaked in different colchicines for different time spans to induce onion tetraploid plants.Morphological identification and stomata size comparison were utilized to undertake ploidy identification.only the onion buds with 0.1%colchicine injected once is successful in inducing 2 onions similar to tetraploid onion.But they both died,so there were no further identification were obtained.Seed soaked in colchicine to induce tetraploid onion:test result showed that 0.15%of colchicine soaking seeds for 72 h had the best induction effect.The induction effect was poor and the success rate was low.Seed germination rate decreased with the increase of colchicine concentration and treatment time period.