| Watermelon（Citrullus lanatus L.）is an important horticultural crop with a refreshing,sweet and juicy taste.EMS（ethyl methane sulfonate）and 60Co-γradiation is two commonly used mutagens that can induce different types of variation in plants.In order to innovate watermelon germplasm resources,in this study,watermelon germplasm M08 was used as the material,and the seeds of M08 radiated with 350 Gy 60Co-γfor 3 hours.Watermelon mutants were screened by observing the agronomic traits of M1 and M2 plants;The M2 generation seeds were screened for salt tolerance during germination to obtain mutants with strong salt tolerance;The M2 generation population of the EMS mutant library constructed in our laboratory was identified and screened.The main results are as follows:1.60Co-γradiation screening of watermelon mutants（1）M08 seeds treated with 60Co-γafter irradiation,the germination rate,seedling emergence rate,and seedling survival rate decreased by 5.88%,18.66%,and 41.96%compared with the control.（2）A total of 1855 plants survived in the M1 population,including 21 types of variation,with a total mutation rate of plants is about 10.57%.Five plants with typical mutant phenotypes were found,namely C1-NO.1（leaf color chimeric mutant）,C1-NO.2（yellow lateral branch and white fruit mutant）,C1-NO.3（pericarp thickening mutant）,C1-NO.4（pericarp thinning mutant）,and C1-NO.5（less seed mutant）.（3）The M2 population survived 247 plants,including 11 mutant phenotypes,with a total variation rate of plants is about 14.17%.By observing the phenotype of M2 generation plants,it was found that only the peel thickness mutants C1-NO.3 and C1-NO.4 can be stably inherited in M2 generation.（4）A male sterile mutant C2-NO.1 was newly discovered in the M2 generation.Its phenotype is that all male flower petals are deformed and anthers are incompletely developed,and can not loosen powder normally.2.Screening of salt-tolerant mutants at germination stage of 60Co-γradiation M08 seeds（1）Under different concentrations of salt stress,the seed germination potential,germination rate,germination index,vigor index,and radicle length decreased compared to the control.According to the linear regression equation,the salt concentration for screening M2 generation seeds during germination was determined to be 240 mmol/L.（2）Using 240 mmol/L NaCl solution to treat 45 M2 generation seeds,only 8 seeds germinated.Through factor analysis,one seed with better salt tolerance than the control was selected.3.Identification and screening of M2 generation population from EMS mutant library（1）The M2 generation mutant population of the existing EMS mutant library in the laboratory was identified,and it was found that only the mutant traits of M1-3（spindle-shaped fruit mutant）and M1-5（green mutant after leaf color）plants were stably inherited in the M2generation.（2）Compared with the control,the leaves of the post-green mutant M1-5 were yellow,and the total chlorophyll content decreased by 52.71%,the net photosynthetic rate decreased by 32.58%,and the intercellular CO2 concentration increased by 25.19%.Later,as the plant grows,the yellow leaves gradually turned green,but the overall color was still lighter than the control.（3）Screening the M2 generation population of the EMS mutant library,three mutants were observed,named M2-1,M2-2,and M2-3.The mutant phenotypes were M2-1:darker peel color and smaller seeds;M2-2:the leaf type becomes narrower and longer,with nectaries evenly distributed on the edge of the leaf,secreting sugar;M2-3:the peel coverage becomes dense. |
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