Effect of Biofertilizer and Drought Stress on Quantitative and Qualitative Traits in Some Winter Rapeseed (Brassica napus L.) Cultivars

To evaluation the effect of plant growth-promoting rhizobacteria under water deficit condition on quantitative and qualitative traits of winter rapeseed cultivars, an experiment was conducted at Agricultural and Natural Resources Research Center located in North Khorasan Province (2015-2017). Plant growthpromoting rhizobacteria (Nitroxin consumption and control) under water deficit condition (after 80, 130, 180 mm evaporation) on quantitative and qualitative traits of winter rapeseed cultivars (Natalie, Okapi, and Neptune) were investigated. Findings indicated that Nitroxin increased soil K, P, Fe, and Cu concentrations and decreased the soil pH and EC. Indeed, the soil N reduction and P increasing trend were related to the maximum biological yield and harvest index (HI) in the second and first years, respectively. Also, an inverse relationship was observed between No. of pods plant-1 (NPP) and No. of seeds pod-1 (NSP) among cultivars. Nitroxin was more affected on NSP and seeds weight than NPP under low and mild drought stress. The highest harvest index was observed in the mild stress in three cultivars, but, the Nitroxin consumption was ineffective. Seed yield and its components except for NPP and HI were increased by the Nitroxin consumption. The HI exhibited the inverse and direct relationship between protein and oil content, respectively. High drought stress compared to low drought stress reduced NPP (54.9%), NSP (1.3%), seed yield (52.2%), biological yield (47.5%), seed oil content (5.5%), seed oil yield (54.9%), and seed protein yield (52.7%). The highest NPP (45.5), seed yield (2740 kg ha-1 ), biological yield (7572 kg ha-1 ), and oil yield (933 kg ha-1 ) were obtained from cv. Natalie. In conclusion, Nitroxin biological fertilizer ameliorates the negative effects of drought stress under mild stressful conditions but it had not any considerable effects on reducing the effects of drought stress under severe stress conditions.