Homogeneous triploid and tetraploid production through crossing with mixoploid parents in pointed gourd (Trichosanthes dioica Roxb.)

This paper elucidates a procedure for isolating homogeneous triploid and tetraploid progeny from mixoploids, which are the most desirable genetic resources to develop genetically stable seedless variety in pointed gourd (Trichosanthes dioica Roxb.) as seeds are unpalatable. All the colchicine concentrations (0.05, 0.1, 0.5%) effectively led to the production of mixoploid for 48 and 72 h exposure time whereas 24 h did not response to induce mixoploid. These mixoploids (female and male) exhibit cross compatability with diploid (female and male) parents for F₁ seed generation. Interestingly, mixoploid parents (either female or male) produced a mixture of normal diploid size seeds and some abnormally large ones, almost twice normal size. Density plot and principal component analysis (PCA) of 603 seeds resulted in separation of diploid, mixoploid and tetraploid accessions involved in different ploidy crosses. To develop a method for the isolation of sexually derived triploid and tetraploid progeny from the induced mixoploids, we examined the ploidy level of F₁ populations by flow cytometry where 18.7% F₁ seedlings were confirmed as triploid and tetraploid progeny when female mixoploid crossed with male mixoploid while 16.7% triploids were isolated crossed with male diploid. These findings suggest that mixoploid female parents were the best options for developing triploid and tetraploid progeny. Overall, the results of this study provide a framework to explore the genetic basis of polyploids isolated from colchicine induced mixoploids in in vivo conditions.