Tetraploid Induction of Watermelon with Herbicide Oryzalin and Identification of the Ploidy

Two inbred lines of diploid watermelon(Tyh08 and Thy32) were used for experiment materia1.The mutagenic effect of tetraploid were studied by using herbicide oryzalin as mutagen in different concentrations(30,40,50,60 mg/L)and different treatment time(1,2,3,4d).The results showed that the mutagenic effect of tetraploid were the best with 50 mg/L oryzalin for 2d in drop seedling and the mutation rates of two lines were up to 15.63% and 17.19%,respectively.The chromosome number of root-tip cell of the variant plants was 44 by the chromosome analysis and so they were identified as tetraploid plants.The leaves of the variant tetraploid plants were obtuse,thick,dark green and had zigzag leaf margin.And the petals were deep yellow,broadened and thickened.By Observing from the microscope,it was found that the stomatal frequency of the leaves obviously decreased,the volume of the guard cells increased.There was difference of the mutagenic effect of oryzalin among various genotypes of materials.