Response to phosphorus deficiency stress among winter rapeseed (Brassica napus L.) cultivars

Due to the vital role of phosphorus as an effective element in plant cell metabolism, it is considered as an important macro-nutrient for plants. Introducing new cultivars of plants that take up and use phosphorus efficiently can reduce financial and environmental cost of phosphate fertilizers. Rapeseed as an important oilseed crop is widely grown around the world, including Iran. This greenhouse experiment was conducted to determine relative use or acquisition efficiency of seven winter rapeseed cultivars (Talaye, Okapi, L72, Gabriela, Karaj, Brutus, Elvis) in deficiently (0 mg P kg-1 add to soil with 4.6 mg Olsen P kg-1 ) and adequately supplied P condition (80 mg P kg-1 add to soil). Shoot and root dry weight, leaf area, root volume, P and Ca uptake in root and shoot and P efficiency was measured and compared. The rhizobag technique was used for accessing rhizosphere soil. Based on the results, cultivars such as Gabriela with higher P uptake efficiency produced more biomass in phosphorus deficiency condition. There was significant variation in PE among the cultivars ranging from 0.25(Elvis) to 0.62 (Gabriela) and PACE ranged from 0.16 (Elvis) to 0.47 (Gabriela) and PUI (g2 SDW mg-1 P) ranged from 0.12 (Elvis) to 0.38 (Gabriela). Interaction effect of soil type (rhizosphere and non-rhizosphere) and P rate on soil pH was significant. It seems that P efficiency and biomass production in these cultivars was primarily due to their acquisition efficiency of P and Ca with larger root system and increase in P mobility and uptake from the soil and P use efficiency was in the next order of importance at P stress environment.