Emergence of ‘Genesis’ Triploid Watermelon Following Mechanical Scarification

This article by John R. Duval and D. Scott NeSmith, University of Georgia Experiment Station, Griffin, appeared in "J. Amer. Soc. Hort. Sci." 124(4):430-432. 1999.

Production of triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] transplants is hindered by poor, inconsistent emergence and frequent seed-coat adherence to cotyledons. Seed-coat adherence leads to weakened and slow-growing plants. High seed costs, coupled with stand-establishment problems, discourage transplant producers from growing this crop. Improvement of triploid watermelon emergence will lessen financial risks to growers and transplant producers, and will provide a more reliable production system.

Mechanical scarification was evaluated as a means to overcome inconsistent emergence and seed-coat adherence. Seeds of ‘Genesis’ triploid watermelon were placed in a cylinder with 100 g of very coarse sand (1.0 to 2.0 mm diameter) and rotated at 60 rpm for 0, 6, 12, 24, and 48 hours in a series of experiments. Number of emerged seed was recorded daily to obtain emergence dynamics.

No significant differences were observed in seed-coat adherence among treatments. The long duration of scarification, however, enhanced emergence, as compared to the control, in three of four experiments. These data support earlier suggestions that a thick or hard seed coat is a factor contributing to poor germination and emergence of triploid watermelons.