| Ground-grown Chrysanthemum has attracted much attention,due to flower characteristics,such as density,long flowering period,dwarf plants,easy breeding,resistance to extensive management and social,economic,and environmental benefits.In recent years,Ground-grown Chrysanthemum were observed with variety in degeneration with plants becoming taller and branching more.Therefore,improving and cultivating Ground-grown Chrysanthemum varieties with dwarfing characteristics must be given importance.In this paper,'Donglinruixue' and 'Pinkling' were employed as experimental materials,to study the mutagenic effects of different doses of radiation on the morphological,physiological and biochemical indexes of plants after 60Co-y ray irradiation.Then,at the cytology level,we observed the abnormal meiotic behavior of the mutant plants,and preliminary explored the cytological effects.Finally,ISSR molecular markers were used to identify the traits of plant variations and to analyze the degree of genetic variation at the molecular level,providing theoretical support for the mutation breeding of Ground-grown Chrysanthemum.The main results show that:1.The semi-lethal(LD50)dose of 'Donglinruixue' was approximately 35 Gy,while'Pinkling' was only 24.44%at 35 Gy.It showed that 'Pinkling' is stronger than 'Donglinruixue'in radiation tolerance.The radiation had a certain inhibitory effect on the plant height of'Donglinruixue'.And the higher the radiation dose,the more significant the inhibition.The effect of radiation on the plant height of 'Pinkling' showed a first increasing and then decreasing.2.After gamma radiation,the leaves morphology,the flower morphology,the petal numbers and the florescence were changed in two kinds of Ground-grown Chrysanthemum,which showed that the number of leaves per plant decreased,the length of leaves and the width of leaves became smaller and the length of petioles became shorter.Meanwhile there were leaves type variations such as increased leaves cracks,leaves with missing green colour,the leaves asymmetric,lanceolate leaves,rolled leaves,leathery leaves and so on.And the leaves type variation rate increased with the increase of radiation dose.The variation of flower morphology showed that the increase of flower diameter and the decrease of pedicel length.The number of tongue-shaped flowers of the two cultivars increased first and then decreased with the increase of radiation dose,while the number of tubular flowers did not change significantly.Meanwhile,the radiation also had an impact on the florescence,but the effects are not the same due to the different varieties.The effects of radiation on the morphology of the flowers of 'Donglinruixue' in the white flower variety was mainly reflected in flower pattern,while flower colour was more likely to occur for the pink variety 'Pinkling' variation.3.After gamma radiation,the physiological indices of two kinds of Ground-grown Chrysanthemum changed greatly.The chlorophyll content of'Donglinruixue' appeared slightly decreased after 60Co-y ray irradiation.At 25Gy,the content of chlorophyll of 'Donglinruixue'significantly decreased while the chlorophyll content of 'Pinkling' showed a certain upward trend.The content of soluble protein decreased with the increase of radiation dose.The MDA content and proline content showed a significant upward trend and the increase of'Donglinruixue' was obviously larger than that of 'Pinkling'.The SOD activity firstly increased and then decreased.The effect of radiation on the POD activity showed increased.The CAT activity of 'Donglinruixue' showed a trend of first increasing and then decreasing while CAT activity of 'Pinkling' showed an overall upward trend.It indicating that the changes of physiological indicators were closely related to radiation sensitivity,'Donglinruixue' strong sensitivity to radiation,so the changes in physiological indicators were also larger after radiation.4.A series of chromosomal aberrations were observed in the two kinds of Ground-grown Chrysanthemum after 60Co-y ray irradiation.With the increase of radiation dose,chromosome aberration rate also increased.The variation types of 'Donglinruixue' included stickiness chromosomes,univalents,unipolarity,laggards,bridges,micronuclei.In the treatment group of'Tinkling' also found meiosis not asynchrony,mebrane outer nuclear and other anomalies.5.ISSR Analysis of variant plants in the two kinds of Ground-grown chrysanthemum.In total,inter-simple sequence repeat analysis produced 72 scorable bands,of which 64(88.89%)were polymorphic in 'Donglinruixue'.Jaccard's coefficients varied from 0.177 to 1.000 with a total average of 0.394.A total of 110 bands were amplified in 'Pinkling',with 93 polymorphic bands(84.54%)and genetic similarity coefficient between 0.337-1.000 with a total average of 0.552.The result of ISSR cluster analysis showed that the clustering results of two kinds of Ground-grown Chrysanthemum were related to the apparent traits,while the relationship between them and the radiation is not obvious.This indicates that the non-directional mutagenicity of radiation cannot induce the change to the same direction even at the same radiation dose.Therefore,it can be considered that gamma rays are an effective induction method for the Ground-grown Chrysanthemum and the mutants can be successfully identified by the ISSR molecular marker technique. |
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