Effects of drought stress on some physiological traits, yield and yield component in four varieties of pumpkin (Cucurbita pepo L.)

For investigation the impact of drought stress on several Agronomic, physiological, yield and yield component in various varieties of medicinal pumpkin (Cucurbita pepo L.), an experiment was conducted as a factorial based on complete randomized block design with three replications at Agricultural and Natural Resources Research Center of Zanjan during spring and summer of 2015. The effects of water stress in five levels ( S1 or control, S2 or irrigation in 75% of Field Capacity (FC), S3 or irrigation in 50% FC, S4 or irrigation in 25% FC and S5 or without irrigation (dry farming )) and four varieties that cultured in multiple points of Iran ( V1 or unknown variety from khoy, V2 or unknown variety from Isfahan, V3 or unknown variety from Zanjan and V4 or var. Styriaca) were considered. The results showed that the effects of drought stress on traits was significant and cause decrease in all investigated parameters. However, the highest grain and fruit yield were obtained in control treatment or full irrigation in Styriaca variety with 825 and 15430 kg.ha-1, respectively and lowest were obtained from Isfahan variety in dry farming condition with 680 and 2758 kg.ha-1 respectively. In the presence of moderate drought stress, the highest rate of photosynthesis, transpiration, stomatal conductance and relative water content was for Isfahan unknown variety and seems that it is a good candidate variety for areas with mild stress.