Mohammad Gerdakaneh - Crops and Horticultural Science Research Department, Kermanshah Agricultural and Natural Resources Research and Education Center, AREEO, Kermanshah, Iran.
Fariba Hoseini - Higher Education Institute of Jahad University of Kermanshah, Kermanshah, Iran.
Nasrin Eftekharinasab - Management of Agricultur jahad of Ravansar, Iran.

In order to evaluate the effect of plant growth regulators on sex determination and yield, an experiment was conducted by spraying different hormonal combinations on medicinal pumpkin. Experimental treatments were included different concentrations of NAA (25, 75, 100, 125 mg/l), paclobutrazol (50, 100, 200 and 300 mg/l) and combination of growth regulators (NAA 25 mg/l + PBZ 50 mg/l), (NAA 75 mg/l + PBZ 100 mg/l), (NAA 100 mg/l + PBZ 200 mg/l), (NAA 125 mg/l + PBZ 300 mg/l), and control (no application of growth regulators). Growth regulators were applied on the plants by spraying at the –two-leaf and four-leaf stages. Results showed that spraying paclobutrazol and NAA caused increase in number of female flowers, fruits per plant, seeds per fruits, 1000 seed weight and seed yield per hectare, but the number of male flowers and ratio of male to female flowers were decreased compared to their values in control plants. The highest fresh and dried seed yield of pumpkin seed was obtained with 50 mg/l paclobutrazol.

NAA, Pumpkinseed, Paclobutrazol, Sex expression, Seed yield