Physiological and Cytological Responses of Watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] to Colchicine Seed Treatment

Abstract

Watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] is a globally significant cucurbitaceous crop valued for its nutritional and refreshing properties. With the growing demand for seedless watermelon, the production of stable tetraploid lines is becoming a critical breeding objective. This study aimed to evaluate the efficacy of colchicine seed treatment in inducing polyploidy and to assess its subsequent effect on germination, mortality, flowering and micromorphological traits. Diploid watermelon seeds were treated with three different concentrations of colchicine (0.05%,0.1%,0.5%) for 24 hours. The results demonstrated a significant dose dependent inhibitory effect on early growth. The increasing concentrations led to delayed germination and a reduction in germination percentage from 93.33% in the control to 53.33% in the 0.5% concentration. The mortality rate also rose with dose reflecting the cytotoxicity of the antimitotic agent. Phenological observations revealed that the treatment induced a substantial lag in reproductive initiation. Greatest delay was in the plants treated with the highest dose in case of both male and female flowers. In contrast the micromorphological analysis showed that with increasing concentration of colchicine the cellular dimensions enhanced. Stomatal length, width, number of chloroplasts per guard cell and pollen diameter increased progressively with higher concentrations. These findings confirm that while colchicine acts as a potent antimitotic agent for inducing polyploidy traits in watermelon, careful optimization of concentration is essential to balance successful induction against physiological stress and mortality.