Influence of arbuscular mycorrhiza fungi and drought stress on fatty acids profile of sesame (Sesamum indicum L.)

Drought stress is one of the most important environmental stresses which influences plant growth and development; and limits plant production. Mycorrhiza-inoculated plants often have greater tolerance to drought stress than non-mycorrhizal plants. In the present study, the effect of drought stress together with arbuscular mycorrhiza fungi (AMF) was investigated on agro-physio-chemical characteristics and oil compositions of sesame. Irrigation level (normal irrigation, mild drought stress, and severe drought stress), and mycorrhizal inoculation (Funneliformis mosseae, Rhizophagus intraradices, and non-inoculated plants) were included as treatments. Combined analysis of variance over 2 years of data revealed that the impact of irrigation and AMF was significant on mycorrhizal root colonization, non-enzymatic antioxidants, leaf phosphorus content, free amino acids and total soluble protein contents, oil yield and compositions, and plant seed yield. Mean comparisons indicated that with increasing severity of drought stress, mycorrhizal root colonization, seed yield, total chlorophyll, total soluble protein, oil yield and percentage, leaf phosphorus, total flavonoid and unsaturated fatty acids diminished. However, the amount of free amino acids, phenol, anthocyanin, carotenoids, saturated fatty acids and the ratio of saturated to unsaturated fatty acids rose significantly. Severe drought stress diminished the seed yield and unsaturated fatty acids levels by about 65 and 10 %, respectively, but it augmented free amino acids by about 65 %. Both AMF species inoculation treatments increased mycorrhizal root colonization, seed yield, oil yield and percentage, total soluble protein, leaf phosphorus, total chlorophyll, unsaturated fatty acids and all non enzymatic antioxidants; however, they reduced saturated fatty acids and the ratio of saturated to unsaturated fatty acids significantly. Thus, for improving quantitative and qualitative traits of sesame, regardless of the drought stress level, AMF inoculation is recommendable.