In Vitro Induction of Tetraploid Mini-watermelon using Oryzalin and Identification of the Ploidy

Three excellent inbred lines of diploid mini-watermelon(048,032 and 047-1) were used for experiment material.The mutagenic effect of in vitro tetraploid induction was studied by using herbicide oryzalin as mutagen in different treatment method,different concentrations and different treatment time.The results showed that the induction rate of tetraploid in vitro depended on treatment method,concentration of oryzalin and duration of treatment.At the same concentration of oryzalin,the induction rate of tetraploid using liquid culture was higher than that using solid culture.The highest induction rate of tetraploid(33.3%) was obtained from the explant cultured in the liquid medium supplemented with 50 mg/L oryzalin for 2d on a rotator.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 variant tetraploid plant was characterized with thick leaf,dark green leaf,compact plant type,short internode,erect stem,smaller leaf shape index.By observing from the microscope,it was found that the density of the stoma obviously decreased,the volume of the guard cells increased,chloroplast number increased.And the petals were deep yellow,broadened and thickened.There was difference of the mutagenic effect of oryzalin among various genotypes of materials.