Evaluation of root mycorrhizal colonization and uptake of some microelements by roots of corns treated with some organic compounds and microbial inoculation

Introduction:

 Rising global demand for food, along with the limitation of arable land, has posed a significant challenge on agricultural researchers to find solutions to overcome this issue. Given that the development of agricultural lands is not practically possible, most attention should be focused on increasing the production yield per unit area. One of the basic approaches to increase crop yield is the consumption of chemical fertilizers, although their application has detrimental effects on humans, soil and the environment. However, organic fertilizers can be considered as a suitable solution to solve this problem. Organic compounds and biomass are the main features of soil fertility and productivity. Applying organic fertilizers such as living compounds (bacteria, yeast, Azolla) and non-living compounds (compost tea, amino acids, humic acid and fulvic acid) can increase soil organic substances. Arbuscular Mycorrhizal Fungi (AMF) are considered as beneficial microorganisms promoting plant growth by establishing a symbiotic relationship with plants. The colonization of plant roots by these fungi increases plant resistance to biotic and abiotic stresses, enhances the plant growth through increasing elements uptake, the improvement of the water flow of plants, and the protection of the plants against diseases. Due to the importance of some food products, such as maize, investigating various aspects of mycorrhizal fungi application and their effect on these products is essential.

Materials and Methods:

 to investigate the effects of some organic compounds and microorganisms on the colonization of AMF and the concentration of some elements, a factorial experiment in greenhouse conditions was conducted in a completely randomized design at three replications for 3 months. The factors included mychorhizal inoculation consisted of Funneliformis mosseae (FM), Rhizophagus intraradices (RI), Rhizophagus irregalaris (RIr), and organic growth enhancers (Azolla, P. fluorescens VUPf5, amino acid complex, humic acid, yeast, bacterial siderophore and compost tea).

Results and Discussion:

 the results showed that the highest root mycorrhizal colonization percentage by Funneliformis mosseae (FM) was observed in bacterial (93%), humic acid (90%) and Azola (76%) treatments. The use of Azola and humic acid and compost tea showed the highest R. intraradices (Ir) root colonization with 96 and 82%, respectively. The highest effect of the treatments on R. irregalaris (Rir) root colonization was observed regarding Azola (96%) and compost tea (90%), respectively. According to the results, the prominent increase in root colonization by three mycorrhizal species was observed in Azola, humic acid, compost tea and bacterial treatments. In addition, the results showed that some compounds increased the concentration of nutrients in the roots and shoots of the treated plants. According to the results, all mycorrhizal species significantly increased the amount of phosphorus in the shoot under the compost tea treatment. Also, the treatment of amino acid combined with R. irregaluris caused an increase in the concentration of iron, compared to the control. The use of R. intraradices along with amino acid increased manganese concentration in the plant aboveground organs by 2.87 times compared to the control. Simultaneous application of siderophore and RI, FM and Rir increased the zinc concentration by 2.16, 2.55 and 1.81 times compared to the control, respectively. The highest uptake of phosphorus, zinc and manganese was observed by R. intraradices soil inoculation and the maximum iron concentration was obtained in plants inoculated with R. irregaluris. The mean comparison of different treatments revealed no significant differences between non-mycorrhiza and mycorrhiza-treated samples, while in comparison with the control, their differences were substantial. Overall, co-treatment of mycorrhizal fungi and Azolla, bacterial and humic acid caused the most significant increase in the mycorrhizal root colonization and the compost tea, amino acid complex and siderophore treatments had the highest impact on the nutrient content of the plant.

In the present study, all treatments had an additive effect on root colonization. However, Azolla, bacteria, humic acid and tea compost treatments caused the most mycorrhizal colonization. These treatments utilized with mycorrhizal fungus had a favourable effect on the growth factors of corn by increasing the rate of colonization. Also, this study revealed that all three species of mycorrhizal fungi increased the concentration of elements and the effect of these fungi along with compost tea, amino acid complex and bacterial siderophore increased colonization and nutrient content in the shoots compared to the control group.