The effect of drought stress and bio-fertilizers on some physiological characteristics and grain yield of medicinal pumpkin plants

In order to study the effects of biofertilizers on the photosynthetic pigments, relative water content (RWC) and grain yield in medicinal pumpkin plants under drought stress condition, experiments were perfumed across two years at research field station of Zanjan University. This experiment was conducted as a split plot based on randomized complete blocks design with three replications. The experiment treatments consisted of drought stress as a main plot in four levels (i.e., control, mild stress, moderate stress and severe stress and biofertilizers as a sub-plot (i.e., no inoculation (control), nitroxin, mycorrhizha and thiobacillus). Results of combined analysis of variance showed a significant association between irrigation regimes and biofertilizers in terms of chlorophyll a, b and grain yield. Under severe stress condition, nitroxin induced 15.78% and 40% growth in terms of chl a and chl b contents and mycorrizha treatment induced 21% and 47% growth in terms of chl a and chl b contents in comparison with the control, respectively. Only mycorrizha treatment had a positive effect on the RWC and carotenoid content (increased 19% and 5.58% in comparison with no inoculation). Regarding positive effects of nitroxin treatment on increasing of grain yield (under moderate and severe stress condition, caused to 13% and 12.6 % increases in grain yield in comparison with the control, respectively), low cost and easy application, use of mentioned treatment can be recommended.