| It’s bad for vigorously carrying out the genetic breeding and selecting and saving excellent germplasm gene resources of Chinese fir because breeding target has limitations, range of variation is narrow under natural conditions and it’s difficult to obtain mutant plants. The research uses seeds collected by the third generation of seed orchard as test material, and carry on Co-gamma irradiate the seeds, and measure morphological indexes, physiological and biochemical indexes, photosynthetic characteristics and chlorophyll fluorescence parameters in Germination of seedlings,3 months of field soil culture period and 6 months of field soil culture period under different dose irradiation treatment in order to further understand and study the mutagenic effect between 60Co-gamma irradiation source and Chinese fir seeds, and select 60Co-gamma irradiation’s suitable irradiation dose range of Chinese fir seeds, and through a series of morphological, physiological and biochemical indicators to further determine the best irradiation dose. The research of Chinese fir seed mutation breeding aims to fully establish mutation system and rich germplasm resources of Chinese fir, broaden mutation type and lay a foundation for genetic improvement of Chinese fir. The main research results are as follows:1 Different irradiation dose has different mutagenic effect for Chinese fir germination period. In terms of the differences between different irradiation dose treatment, electrical conductivity after 12h, absolute conductivity and relative conductivity show little change when irradiation dose below 12Gy; The three conductivity show slowly rising trend when irradiation dose exceeds 12Gy; The viability of seed is largest on 9Gy dose, within the scope of the 9-20Gy irradiation dose, the seed vigor partially lost and is declining along with the increase of irradiation dose, when the irradiation dose of 20--30Gy, the number of completely deactivation seeds significantly increase and the seed vigor is significantly inhibited; Under 25Gy and 30Gy irradiation dose,60Co-gamma rays have significantly inhibition effect on Chinese fir seeds, and contents of root of seeds turn black and the seeds dead completely in the germination stage. Compared with the control treatments, tow dose (3Gy) irradiation promote seed germination, and germination rate is reduced when irradiation dose greater than 6Gy, and the decrease of germination rate is along with the increase of irradiation dose; Chinese fir seeds have a high sensitivity to mutation, the research shows range of the suitable irradiation dose was 9-16Gy;2 Different irradiation doses have different mutagenic effect for Chinese fir field seedlings after 3 months.9Gy irradiation dose has the best comprehensive effect on growth and biomass index of Chinese fir seedlings, specific performance in:the value of seedling height, root length and fresh weight is the largest in 9Gy irradiation dose; seedling ground diameter is the largest in 12Gy dose,9Gy is next; the number of seedling root is maximum in 6Gy dose,9Gy and 12Gy are slightly lower; seedling high growth of 3Gy and 9Gy dose is higher than control group, and root length increase of 6Gy and 9Gy dose is higher than control group.9Gy dose have the best comprehensive effect on enzyme activity and MDA content for Chinese fir, specific performance in:SOD enzyme activity has the maximum peak value in 3Gy irradiation dose,9Gy dose is next; CAT enzyme activity has the maximum peak value in 9Gy irradiation dose,12Gy and 3Gy dose is next; POD enzyme activity has the maximum peak value in 6Gy irradiation dose,9 Gy dose is next; PPO enzyme activity has the maximum peak value in 12Gy irradiation dose,9Gy dose is next; MDA content has maximum peak value in 9Gy irradiation dose,6Gy and 12Gy dose is next.3 Different irradiation doses have different mutagenic effect for Chinese fir field seedlings after 6 months. Different irradiation dose has different effect on photosynthetic characteristics of Chinese fir seedling leaves, specific displays in:Content of chlorophyll a and the chlorophyll content have a very significant positive correlation with irradiation doses, Content of chlorophyll b and chlorophyll-a/b are not significant; Fo has a very significant positive correlation with irradiation doses, Fm, Fv, Fv/Fm and Fv/Fo have a very significant negative correlation with irradiation dose; Irradiation has little effect on net photosynthetic rate and intercellular CO2 concentration, and net photosynthetic rate and intercellular CO2 concentration are not significant with irradiation doses, but stomatal conductance and transpiration rate have a very significant negative correlation with irradiation doses. Different irradiation dose has different effect on protective enzyme activity and MDA content of Chinese fir seedling stems, roots and leaves, specific displays in:SOD enzyme activity has a very significant correlation with irradiation doses of Chinese fir stems and roots, but is not significant of leaves; POD enzyme activity, CAT enzyme activity and PPO enzyme activity are not significant with irradiation doses of Chinese fir stems, roots and leaves; MDA content has a very significant correlation with irradiation doses of Chinese fir leaves, but is not significant of stems and roots.4 The main effect factors affecting mutagenic effect of Chinese fir reflect in three aspects: Firstly, the index of growth characters; secondly, the index of the protective enzyme activity and MDA content; thirdly, the index of the chtorophyll fluorescence parameters and photosynthetic rate. According to scores and comprehensive scores of principal component, the score of 9Gy in the second principal component is the highest value, and in the first and third principal components in size 4 and 2, respectively. And comprehensive score of 9Gy is highest and is significantly higher than the other groups. All of these show that 9Gy irradiation dose has the best conprehensive effect on the index of growth characters, the index of the protective enzyme activity and MDA content and the index of the chlorophyll fluorescence parameters and photosynthetic rate. In addition,9Gy irradiation dose has better effect on the other physiological and biochemical indicators. Consequently, Co-gamma rays have better mutagenic effect on Chinese fir seeds under 9Gy irradiation dose.5 Different irradiation doses have different effect on the rate and type of aberration on different Chinese fir growth stage (seed germination period, soil culture period of 3 months and 6 months soil culture period). In seed germination period, the main type of aberration include: radicle root to become red, radicle root swelled, radicle root coking, radicle and seed separation and root bifurcation; in soil culture period of 3 and 6 months, the main type of aberration include: etiolated seedling, albinistic seedling, branched and dwarfing seedlings. Among them, the dwarf type of aberration accounted for the vast majority. The partial aberrant seedlings are death with the growth of Chinese fir seedlings. On the whole, the mensuration results of Chinese fir in different growth stage show that Chinese fir seed mutagenic effect caused by Co-gamma irradiation isn’t along with the growing of plants disappear entirely, and some of these indicators still affect the growth and development process, photosynthetic efficiency and morphological characteristics of Chinese fir, and whether this effect will continue and whether can be genetic remain to be further discussed. |
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