Seed treatments and orientation affects germination and seedling emergence in tetraploid watermelon

Polyploid watermelon has poor germination and low seedling vigor mainly due to thick seedcoat and seedcoat adherence to emerged cotyledons. Seed treatments nicking at radicle end and soaking in distilled water, hydrogen peroxide (1 or 2%), gibberellic acid (0.5 or 5 mM), benzyladenine (0.5 or 5 mM) and potassium nitrate (3%) were applied to seeds of SS-8 and SS-I I lines of tetraploid watermelon. Seeds were soaked for 4 hours followed by drying for 5 days at 20 degrees C with 40% relative humidity and germinated in Petri plates at 30 degrees C. Seed treatments, nicking, presoaking in distilled water or H2O2 enhanced the germination of tetraploid seeds but showed genotypic variation. Early seedling emergence after 4 days Occurred in line SS-8 with nicking, GA(3) (5mM) and H2O2 (2%) treatment but line SS-11 acquired comparatively more time for seedling emergence. Seed planting orientation affected both seedling emergence rate and seedcoat adherence. Seed positioned with radicle up reduced the seedcoat adherence to cotyledons. A genotypic variation was observed regarding growth characteristics; however, 2% H2O2 treated seeds showed better growth of seedlings.