Invigoration of watermelon T₁ tetraploid seeds using priming Treatments

Tetraploid line development is beset with poor germination and seedling vigour of tetraploid seeds primarily due to thick seed coat and under-developed embryo. Tetraploid (T°) seeds generated through colchicine application on three watermelon genotypes (Sugar Baby, California Sweet and 5255-1-3-1) were subjected to priming treatments viz; Gibbrellic acid (GA₃) @ 100 ppm, Ethrel @ 100 ppm, Potassium nitrate (KNO₃) @ 1% and Potassium dihydogen orthophosphate (KH₂PO₄) @ 10⁻² M for 12 and 24 hours, respectively. Seeds primed for longer duration i.e. 24 hour exhibited better germination and growth characteristics than their respective 12 hour priming treatments. Seeds invigorated with KH₂PO₄ for 24 hours had the greatest germination (67.47%) and longest seedlings (10.423cm plumule, 7.261cm radicle). Ethrel @ 100 ppm for 24 hours produced the seedling having the highest dry weight (0.125g). Non primed seeds fared poorly in all parameters. California Sweet responded best to seed priming treatments (65.21% germination; 0.124g, seedling dry weight). In a first report, KH₂PO4 priming treatment can be effectively used to enhance the emergence and other seed attributes of tetraploid watermelon in early generations.