Effect of Mycorrhizal Fungus (Glomus spp) on Wheat (Triticumaestivum) Yield and Yield Components with Regard to Irrigation Water Quality

Decrease in water quality affected by salinization of the water resources due to the drought is one of the limiting factors of plant production. Using mycorrhizal fungi is an important approach to deal with damaging effects during stress conditions. The symbiosis of arbuscular mycorrhiza (AM) with the host plant and hence, the production of a very extensive network of hypha, enhances nutrient acquisition and improves water uptake in the host plant. The specialized network of hypha raises the uptake and translocation of nutrients to the plant, whereas it inhibits high uptake of Na and Cl and their transport to plant shoots compared with plant roots. Hence, AM can alleviate the stress of salinity on plant growth and increases their tolerance to the stresses. In order to evaluate the influence of mycorrhizal fungi on yield and yield components of wheat, a greenhouse experiment was conducted in research farm of Shahid Chamran Ahvaz University. Experimental design was a randomized complete block design arranged in split factorial with three replications. The factors were water salinity (water quality) including filtered water (EC ≥ 1 dS m-1), tap water (EC = 1/7-3 ds m-1), tap water plus NaCl and filtered water plus NaCl (EC = 8 ds m-1). Soil sterilization included sterilized and non-sterilized soil and mycorrhizal inoculation were in five levels (non-inoculated, inoculated with ‌Glomusmosseae, G. intraradices, G. geosporum and mixture of them). Yield and yield components were measured at crop maturity and colonization percentage of root was determined at flowering stage. Root colonization by AM was determined through preparing root samples at 1 g in each experimental unit, and roots were stained using the Gridline- Intersect Method. The harvest index and mycorrhizal dependency were also measured. Salinity levels determined approximate the threshold of wheat –tolerate- salinity before the results would rather reflect saline stress on mycorrhizal symbiosis than on wheat plants. The results showed that salinity decreased colonization percentage and grain number per spike but it did not affect yield and yield components significantly. In non- inoculated soil, the formed mycorrhizal symbiosis by indigenous fungi improved colonization percentage, while it did not result in significant differences of the yield and its components. The inoculation with mycorrhiza fungi was successful. Mycorrhizal colonization rates of 15-32% and mycorrhizal dependency rates of 7-13% were observed in the inoculated treatments, and this effect led to significantly higher grain yield, spike number and grain number per plant in compare with control. Furthermore, there was a significant interaction on colonization percentage and whole yield components between AMF inoculation and salinity except for spike number. Spike per plant, grain number per spike and colonization percentage affected by mycorrhizal inoculation in interaction with soil sterilization. Colonization percentage was positively correlated with spike number, grain number per plant and grain yield (significant at α=1%). Enhanced yield under all mycorrhizal treatments related to higher grain number per plant, whereas there was no significant difference between these treatments for grain weight. Although the colonization levels of individual mycorrhizal treatments were generally lower, the fostering of grain yield was even strongly more pronounced than with mixed mycorrhizal treat (significant at α=1%). Effects of salinity and soil sterilization varied depending on the species of fungi and water quality. In comparison with other mycorrhizal treatment, G. geosporum showed higher salt tolerant relatively on display of superior colonization percentage and grain number per plant in salinity with tap water; and the colonization percentage by G. mosseae was not affected by soil indigenous fungi. The results showed that salinity decreased colonization percentage of inoculated mycorrhiza besides indigenous fungi, whereas mycorrhizal dependency was not influenced by salinity levels. Mycorrhizal dependency would probably provide a more consistent basis for the relative benefit provided by mycorrhiza at the saline condition than the colonization percentage. Reductions of the mycorrhizal dependency to wheat plants caused by increasing soil water or nutrient availability however enhancement of plant growth have been indicated especially when mycorrhizal wheat plants exposed to saline stress.