Influence of three species of Arbuscular Mycorrhizal Fungi on growth and nutrients uptake in zinnia plant under drought stress conditions

Drought is one of the major environmental constraints that limit plant growth and productivity more than any other environmental factor. Drought stress reduces normal growth, disturbs water relations and nutrition uptake in plants. Arbuscular mycorrhizal fungi (AMF) can increase plant tolerance to drought via direct water uptake and transport through fungal hyphae to the host plants, enhance nutrient uptake, improve osmotic adjustment and antioxidant activity. This study was conducted to evaluate the influence of three AMF species (singly or in combination) on DS alleviation of zinnia seedlings (as a potentially drought-tolerant flower crop) grown under different DS levels. To study the effects of three identified isolates of arbuscular mycorrhizal fungi (AMF) on growth and elements concentration (P, K, Fe, Zn, Cu and Mn) of zinnia plants (Zinnia elegans L. var. Magellan Red) under drought stress condition, a greenhouse experiment was conducted with two factors including mycorrhiza at five levels (no mycorrhizae as control, Rhizophagus irregularis, Rhizophagus intraradisces, Funneliformis mosseae, Mix ) and four levels of drought stress (100% FC as control, 80% FC, 60% FC and 40% FC) with six replicates based on a completely randomized design (CRD). Seedlings with four true leaves were transplanted into 1 L pot and immediately inoculated with 210 spores per pot of the each of above symbionts. Control plants received the same amount of autoclaved inocula. The plants were irrigated with distilled water for 50 days to obtain certain amount of infection; then four irrigation regimes were achieved for four weeks. According to the results, vegetative growth traits like fresh and dry weight of shoot, root and flower leaf area and flower diameter were reduced significantly with increasing drought stress levels. Drought stress reduced uptake and transport of elements. The utilized AMF improved growth and nutrients uptake under drought stress considerably in 40% FC where R. irregularis, R. intraradisces, F. mosseae and mix increased dry weight of shoot by 20, 22, 20, 11 percent respectively in comparison with control. In conclusion, it is suggested that AMF inoculation improves drought tolerance of zinnia plants at least in part through the enhanced uptake of slowly diffusing mineral ions such as PO42- and Zn2+. Moreover, arbuscular mycorrhizal colonization provides better osmotic adjustment which can be correlated with K+ accumulation in top portions of inoculated plants. The results of this study showed that zinnia plants exhibited a better symbiotic relation with three identified isolates of arbuscular mycorrhizal fungi especially with mixed treatment.