Effect on Mycorrhizal Fungi Symbiosis and Priming on Yield and Yield Components of Sesame Seeds at Levels of Drought Stress

Drought stress is one of the most important factors limiting growth and crop production in the arid and semi-arid world. Plant response to drought stress depends on the type, severity, and duration of stress, plant species, and stress occurrence stage and farm management.
The sesame, among crop plants, is resistant to drought and heat stress and has great importance in the agriculture development of arid and semi-arid region for summer planting. But this plant is sensitive to drought stress at seedling stage and during flowering to grain filling. To overcome the drought stress, the biological solution is one of the basic strategies that should be considered and can be noted the mycorrhizal fungi. One of the most important types of mycorrhizal is arbuscular rmycorrhizal Fungi, which is important in terms of agriculture; because most crops and horticultural ability to coexist with this type of mycorrhiza. In order to evaluate the effect of irrigation levels and arbuscular mycorrhizal fungi symbiosis on yield and yield components of sesame, an experiment was carried out as split-factorial based on a randomized complete block design with three replications at Agricultural Research Station of Haji Abad, Hormozgan province, Iran during growing season 2014-2015. Experimental factors included: drought stress as main factor in 3 levels: 100% water requirement (normal irrigation), 70% water requirement (moderate stress)and 50% water requirement (Severe stress), the priming as sub factor in 3 levels: without priming (control treatment), hydropriming and osmopriming and the mycorrihizal fungi application as other sub-factor in 3 levels: [without mycorrihizal fungi application(control), mycorrihizal fungi application (Glomus mosseae) and mycorrihizal fungi application (G. intraradices). Analysis of variance data showed that the effect of drought stress had significant effect (P≤0.01) on all traits were studied. The effect of mycorrhizal inoculation was significant on measured plant responses (P≤0.01). Priming treatments were significant on seed number per capsule (P≤0.01) and thousand grain weight and grain yield, biological (P≤0.05). Interaction effects of mycorrhiza × irrigation was only significant on grain yield (P≤0.05), the effects of the interaction of mycorrhiza × priming on seed number per capsule (P≤0.01) and the thousand grain weight (P≤0.05) were significant. The results also showed that the highest grain yield and all measured traits obtained when using irrigation water requirement by 100 percent (normal irrigation). Inoculation with mycorrhizal fungi species G. mosseae and G. intraradices compared to lack of mycorrhizal fungi (control treatment) improved yield by 10.4 and 4.7 percent. Priming treatments compared to non-primed (control treatment) increased seed yield by as much as 2 percent. Drought stress decreased sesame yield, however, the using mycorrhizal fungus can be reduced that effect. The effect of two species of mycorrhizal on sesame yield and their effect on reducing stress damage was different; So that mycorrhizal symbiosis G. mosseae has more than the G. intraradices and avoided the sharp drop in sesame yield in drought stress treatments. The results of this study showed that drought stress and water shortage decreased significantly yield and yield components of sesame. Mycorrhizal fungi improved the absorption of moisture and nutrients under water stress and increased plant resistance to water stress, therefore increased yield and yield components of sesame. The species of G. intraradices fungi compared to G. mosseae was more efficient in terms of resistance to water stress. Thus, it seems that mycorrhizal, in addition to improving the yield due to increased root system development and consequently increasing the availability of moisture and access to nutrients, can have a positive effect on reducing the effects of irrigation deficiency on sesame plants. Seed priming, due to better germination, rapid seedling growth, proper establishment and, finally, the optimal use of nutrients and environmental factors, ultimately increased yield.