Changes in Seed Oil Yield and its Components of Black Mustard (Brassica nigra L.) as Affected by Rhizobacteria and Growth Regulators under Cadmium Stress Conditions

Cadmium is one of the soil primary pollutants which is categorized as heavy metals and brassicaceae family are able to accumulate high amounts of heavy metals such as cadmium by producing high amounts of dry matter. In order to evaluate fatty acids variation, seed oil percentage, yield and yield components of black mustard as affected by growth promoting rhizobacteria and growth regulators under cadmium stress condition, a factorial experiment based on randomized complete block design was conducted at the Research Green House of Mohaghegh Ardabili University with four replications. Experimental treatments were two cadmium levels (0 and 100 milligrams per kilograms of soil), three rhizobacteria levels (control, Azospirillum and Pseudomonas) and three growth regulator levels (control, salicylic acid and brassinosteroid). Mean comparisons indicated that cadmium treatment decreased pods number per plant, grain number per pod, root dry weight, seed oil percentage, oleic, linoleic, eicosenoic and erucic acid percentages, significantly. Growth promoting rhizobacteria increased all of above mentioned parameters significantly, where as, it decreased palmitic acid content. Plant growth regulating sprays resulted in a significant increment in plant yield, shoot and root dry weight, seed oil percentage and all kinds of unsaturated fatty acids while it reduced stearic acid content and saturated fatty acids. The interaction of cadmium×rhizobacteria indicated that both cadmium levels used, along with rhizobacteria treatment, increased plant yield, thousand seed weight, shoot dry weight, linolenic acid and unsaturated fatty acids, where as decreased stearic and saturated fatty acids, significantly. In general, the effects of cadmium on these traits were different. Interaction of cadmium×growth regulators, spray application of growth regulators, under both cadmium levels, reduced palmitic acid and induced unsaturated fatty acids significantly and cadmium application had an inverse result.