Preliminary Study On EMS Mutagenesis And Screening Of Cold-tolerant Mutant In Hibiscus Hamabo Sieb.et Zucc

Hibiscus hamabo Sieb.et Zucc,which belongs to the malvaceae family,is an important deciduous shelter-forest species with strong resistance to salt,drought and flood stress.In this study,Hibiscus hamabo seeds and ethyl methyl sulfonate(EMS)of different concentrations were used as raw materials and mutagen,respectively,the semi-lethal dose(including appropriate concentration and treated time)of EMS was determined by the indicators such as germination potential,germination rate and germination index of the seeds.Then,through observation of variation phenotype,determination of physiological indexes and comparison of submicroscopic structure of Hibiscus hamabo Sieb.et Zucc seedlings,cold-tolerant mutants were screened and identified so as to obtain new Hibiscus hamabo Sieb.et Zucc germplasm with cold tolerance.The results are as follows:1.Effects of EMS on seeds germination of Hibiscus hamabo Sieb.et Zucc(1)The seed germination of Hibiscus hamabo was inhibited by EMS at different concentrations.The results showed that the degree of inhibition of seed germination aggravated with the increase of EMS concentration and the time of mutation treatment.According to the germination rate,germination potential,germination index and seedling rate of the seeds,the semi-lethal dose of EMS treated Hibiscus hamabo seeds was determined to be 1.5% EMS for 4h.(2)The treatment of EMS caused certain physiological damage to Hibiscus hamabo Sieb.et Zucc seeds.The electrical conductivity and MDA content of the seed extract increased with the increase of EMS concentration and treatment time.The effect of EMS on seed germination of Hibiscus hamabo also showed that the seedling radicle and root lengths were in hibited.2.Effects of EMS mutagenic treatment on morphology and leaf surface structure of Hibiscus hamabo Sieb.et ZuccMany morphological variants appeared in the Hibiscus hamabo Sieb.et Zucc seedlings germinated from the seeds treated by EMS.The variation types mainly include plant height,leaf type,leaf color and flowering period.(1)Plant height mutation: The average plant height of the control was 19.68 cm,while the average for mutant plant height was 3.84 cm.(2)plant-type variation: Hibiscus hamabo seedlings induced by EMS had three creeping mutants and multi-branching mutants,and the horticultural traits were obvious.(3)Leaf mutation: In the M1 generation,Leaf mutation traits contained leaf morphological variation and leaf color variation.The shape of the control leaves were ovoid,The leaves of the mutant plants were curly leaves,heart-shaped,tlip tree leaves.Two mutant plants have three cotyledons;Leaf color variation plants have yellowing leaves,mosaic.(4)Anthesis early mutantion: Under normal growth conditions,the Hibiscus hamabo can blossom and bear fruit in 2-3 years of seedlings,while 4.65% of the Hibiscus hamabo treated with 1.5%EMS mutagenesis showed early flowering.(5)Blade scanning structure observation: The stellate hairs on the leaf surface of the mutated plants decreased,the number of stellate hairs branching decreased.3.Effects of low temperature stress on physiological indexes of Hibiscus hamabo Sieb.et Zucc.seedlings(1)Semilethal low temperature: Study on Hibiscus hamabo electrolyte leakage and semi-lethal temperature during low temperature stress,When the temperature goes down,the leaf electrity conductivity rise,according to the electrity conductivity to determine the median lethal temperature is-10? treatment 8 h.(2)Screening of cold resistant mutants in Hibiscus hamabo Sieb.et Zucc: Under low temperature stress,it was found that the enzyme activities were increased,and the mutagenic strain was significantly higher than the control group.The soluble protein and proline osmotic showed the same trend,and the MDA content wasopposite to the trend of antioxidant enzyme and osmotic substance.This indicated that EMS mutagenesis could improve the ability of plants to resist cold stress.4.Observation of ultrastructure of leavesThe leaf ultrastructure of the cold-resistant mutants was observed under cold stress.It was found that under the same cold stress treatment,EMS mutagenesis could keep better chloroplast morphology and accumulate more starch grains under low temperature stress,while the mitochondrial structure of the mutagenesis plant and the control plant had no obvious change under low temperature stress.The results of electron microscopy were consistent with those of physiological indexes.