Phenotypic Analysis And Molecular Identification Of EMS Mutagenic Watermelon Mutants

The creation of new varieties has always been the focus of watermelon germplasm resources research,and it is also the cornerstone of breeding research.Using mutagenesis technology to formulate watermelon mutants,obtain new watermelon breeding materials,and enrich the diversity of existing resources is of great significance to watermelon breeding research and practical production.In this study,the highly inbred line of watermelon variety’W-17-FGFB’and’W-03-05-core’was used as the experimental material and treated with EMS（Ethyl methane sulfonste）to construct a watermelon mutant library by optimizing the mutation technology system.The mutant plants were screened by observing the agronomic traits of the M₂plants and the important agronomic traits were further identified by SSR molecular markers.This work can enrich the germplasm foundation for the germplasm resource innovation of watermelon.The main results are as follows:（1）Five EMS concentration gradients（0,0.5%,1.0%,1.5%,and 2.0%）combined with three mutation times（12 h,16 h and 24 h）were used to evaluate the effects of different mutated conditions on germination rate and seedling emergence rate.The results showed the EMS concentration of 2.0%with 24 h was the best condition for creating the mutant.（2）By analysing the agronomic characters（including stems,leaves,flowers,fruits and seeds）,20 variation types were observed in the mutant plants of’W-17-FGFB’.The mutated rate accounted for 26.02%with 64 mutants observed in the M₂plants.The mutation rate accounted for 26.02%of the total number of plants of M₂generation.As for the variety of’W-03-05-core’,16 variation types were observed in the mutant plants.The mutated rate accounted for 22.89%with 38 mutants observed in the M₂plants.（3）The DNA of the wild type and M₃mutant of the two varieties were mixed respectively to be sequenced and developed the 26 pairs of SSR primers.Then,14 pairs with high polymorphism,good stability and comprehensive performance were used to analyze the 13 typical mutations of’W-17-FGFB’and 8 typical mutations in the M₃plants.The results showed there were different sites,band deletion or increase existing in the mutant compared with the wild type,indicating there has variation at the DNA level in each mutant of the two varieties.