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Introduction Wheat (Triticum aestivum L.) is one of the oldest and most widely used crops in the world and is the most important source of human food that grows in a wide range of climatic conditions in the world. In arid and semi-arid regions, water is the main limitation. Iran is a dry and semi-arid country with limited precipitations. Therefore, the mean annual rainfall in Iran is even less than one third of the global average. There are many solutions for sustainability in agriculture, one of which is the use of biological fertilizers. Among these biofertilizers are mycorrhizal fungi. The symbiotic relationship between the arbuscular mycorrhizal fungus and the roots of the host plant significantly increases the growth and absorption of plant nutrients. In this research, the aim is to investigate the effect of arbuscular mycorrhizal fungus on improving the yield, yield components, and chlorophyll index of wheat by applying water deficit stress through increasing the interval of irrigation cycles. Materials and Methods This factorial experiment was conducted based on a randomized complete block design in four replications in the research farm of the Azad Islamic University of Miandoab, northwestern Iran in 2021. The experimental factors included the application of arbuscular mycorrhiza fungus species in three levels, control (without inoculation), inoculation with Glomus mosseae and inoculation with Glomus intraradices and three levels of irrigation regimes (i.e. irrigation after every 6, 13 and 20 days). Seeds of Elvand wheat cultivar were inoculated with mycorrhizal fungus, then the inoculated seeds were immediately planted into a depth of 3. Before planting, 15 tons/ha of manure and 25 kig of nitrogen fertilizer in the form of urea were uniformly applied to the soil. During the growing season, 50 kg of nitrogen fertilizer in the form of urea was used during the two stages of stem growth and spike formation. To measure wheat grain yield components, 10 plants were harvested and to determine grain yield and plant above- ground dry mass, 0.25 m-2 was taken from each plot. In this way, after removing two rows from each side and half a meter from the beginning and end of all rows as a margin, sampling of experimental units was done. The evaluated traits included the spikes/plant, grains/spike, the thousand-grain weight, plant aboveground dry mass, grain yield, harvest index, and greenness index Results and Discussion Results indicated that the effect of irrigation intervals and mycorrhiza fungus were significant for grains/spike, thousand-grain weight, grain yield, above-ground dry mass, harvest index, chlorophyll index, photosynthetic pigments and proline concentrations. G. mosseae species increased the grains/spike, thousand-grain weight, above-ground dry mass, harvest index, and chlorophyll concentration compared to G. intraradices species by 5.21, 9.73, 8.86, 6.96 and 4.08% and increased the above-mentioned attributes compared to the control by 29.94, 30.28, 39.68, 27.90 and 21.43%, respectively. The highest spikes/plant, grain yield, chlorophyll index and concentration of chlorophyll a belonged to irrigation interval of 6 days and inoculation with G. mosseae species with 6.34, 612.45 g m-2, 62.89 SPAD unit, and 0.306 mg g-1 FW, respectively. Prolongation of irrigation interval by creating water deficit stress caused the sterility of the spikes and significantly reduced the grains/spikes. The irrigation regime had a significant effect on the grain yield and by reducing the irrigation intervals, the grain yield was increased. The drought-induced decrease in grain yield stemmed from the decrease in green index, chlorophyll concentration, spikes/plant and grains/spike, leading to decrease in the harvest index. With increase in the irrigation interval, the concentration of chlorophyll a and b decreased, but the mycorrhizal inoculation led to significant increase in the concentration of chlorophyll a and b under water deficit stress. The plants inoculated with mycorrhizal fungus suffered less from water deficit stress than the non-colonized plants, and as a result, the concentration of proline increased less compared to the plants deprived from mycorrhizal fungus. According to these results, irrigation of wheat plants every 13 days and application of G. mosseae can produce the desirable grain yield, while decreasing water consumption for wheat production. Conclusions Mycorrhizal fungus increased the plant's resistance to drought stress by improving the absorption of water and nutrients under water stress deficit. G. mosseae was more effective in increasing the resistance of wheat against water deficit stress and as a result, it increased the grain yield, yield components, chlorophyll index and chlorophyll concentration of wheat to a greater extent compared to G. intraradices. In order to make the best use of water resources and soil nutrients, irrigation of wheat should be done every 13 days and must be accompanied by inoculation with G. mosseae to achieve an acceptable grain yield. [ABSTRACT FROM AUTHOR] |
