HIGH-FREQUENCY SHOOT REGENERATION FROM LEAF EXPLANTS OF MUSKMELON

Efficient in vitro plant regeneration systems are critical for many pu rposes including plant transformation. Current regeneration systems fo r melon (Cucumis melo L.) plants generally utilize cotyledon explants; regeneration from melon leaves has received limited attention. We inv estigated several factors that influence regeneration from melon leave s including: genotype growth conditions and age of the source plant, l eaf age, explant orientation, gelling agent, and the addition of silve r nitrate and sulfonylurea herbicide to the culture media. Critical fa ctors that influenced regeneration were preculture conditions of the d onor plants, leaf size, and the use of silver nitrate and Phytagel in the medium. The best results were obtained with 3-4 cm diam leaves exc ised from pot grown greenhouse or growth chamber plants cultured on MS medium with 5 mu M IAA, 5 mu M BA, 1 mu M ABA, 30 mu M silver nitrate and 2.6 g l(-1) Phytagel. Low concentratons of sulfonylurea herbicide (0.25 mg l(-1) DPX-M 6316) also enhanced regeneration. Under optimize d conditions 80 - 100% of the explants regenerated, with 10 - 100 shoo ts per explant.