FLOW CYTOMETRY OF DNA CONTENTS OF COLCHICINE TREATED WATERMELON AS A PLOIDY SCREENING METHOD AT M1 STAGE

Flow cytometric analysis of DNA content in watermelon was conducted to identify tetraploids among colchicine treated seedlings and to compare flow cytometry with other methods of ploidy screening such as chloroplast number in stomata guard cells, chromosome counts, leaf area, flower size, pollen colpi and seed characteristics. Flow cytometric analysis proved rapid and convenient to detect tetraploids compared with chloroplast Counts. DNA index and chloroplast number were highly correlated. Number of chloroplasts in guard cells ranged from 5-7 and 10-12 in diploids and tetraploids, respectively but it was impossible to differentiate chimeras by chloroplast counts. Chromosome counts were tedious while other methods needed more time to identify tetraploids. Higher leaf area and larger flower size, and 4 colpi in pollen of tetraploid plants against 3 colpi in pollen of diploid were observed. Tetraploid seed showed larger size and thicker seedcoat and partially filled seed cavity due to less developed cotyledons as compared to diploids.