Morphological and anatomical characterization of colchicine-induced polyploids in watermelon

Abstract

This study aimed to elucidate the effective colchicine concentration to induce polyploidization distinction based on morphological and anatomical features in watermelon. Watermelon seeds were soaked in different colchicine concentrations (0.05, 0.1 and 0.5%) for several durations (24, 48 and 72 h) to induce polyploidization. Putative polyploids were evaluated regarding their morphological and anatomical traits compared to diploids (control). A colchicine concentration of 0.5% for 72 h resulted in the lowest germination percentage with high mortality in putative polyploids compared to in diploids. Morphological traits revealed vigorous growth in putative tetraploids with slower germination speeds, whereas the putative octoploids had suppressed growth compared to tetraploids and diploids. Regarding reproductive biology, the petal number (6), pollen size and viability were remarkably higher in induced polyploids, which confirmed successful tetraploid induction by 0.5% colchicine treatment for 72 h. Similarly, a bigger stomatal size with a lower density was also noticed in induced tetraploids compared to in diploids using the same treatment after anatomical analyses. Meanwhile, a PCA and correlation matrix illustrated that, among the 20 variables, polyploid induction efficiency (PIE), leaf length (LL), guard cell distance (GCD), and pollen viability (PV) were recognized as the most effective morphological and anatomical indicators for successful polyploid induction confirmation with colchicine in watermelon. The present findings provide a basis for distinguishing colchicine-induced polyploids as improved genetic resources to enhance seedless triploid breeding in watermelon.