Abstract
The use of bio-fertilizers in agro-ecosystems is considered to have the potential to improve plant growth in extreme environments featuring water shortages. However, while arbuscular mycorrhizal fungi (AMF) and bacteria bio-fertilizers have been used in other plants to enhance stress tolerance, little is known about their symbiotic effect on sorghum (Sorghum bicolor L.) growth under drought stress conditions. Therefore the aim of this study was to investigate the inoculation of sorghum with Nitroxin and Glomus mosseae and their interaction effects on the agro-physiological characteristics and grain yield of sorghum under drought stress conditions. Nitroxin is a bio-fertilizer that consists of a mixture of Azospirillum and Azotobacter bacteria. The results showed that co-inoculation of sorghum seeds with Nitroxin and AMF improved the chlorophyll (a, b and total) content, soluble proteins, water use efficiency) WUE(, relative water content (RWC), nitrogen (N) content in the plant, AMF spore density, proline content, grain yield, panicle length, the number of panicles per plant, grain number per panicle, 1000-grain weight and decreased the electrolyte leakage and water saturation deficit (WSD) in drought stress and non-stress conditions. Under drought stress conditions, there was a 27% increase in grain yield under the synergistic effects of bacteria and fungi compared to the non-application of these microorganisms. The results of this experiment show that Nitroxin and AMF bio-fertilizers can mitigate the negative effects of stress on plants in drought stress conditions by increasing the amount of photosynthetic pigments, soluble proteins and osmotic regulation and decreasing electrolyte leakage. We found that the combination of bacteria and AMF for sorghum growth and yield increment is a promising method to cope with the stress caused by drought.
Highlights
Drought stress is a challenging issue for crop production problems in arid and semi-arid regions of the world [1]
The results of the means comparison showed that increasing drought stress levels significantly decreased the chlorophyll content of the sorghum plants while all treatments of inoculation with the bio-fertilizers improved the chlorophyll content
We found that sorghum growth was clearly increased when the arbuscular mycorrhizal fungi (AMF) was associated with rhizobacteria (Azospirillum and Azotobacter)
Summary
Drought stress is a challenging issue for crop production problems in arid and semi-arid regions of the world [1] This type of stress reduces the growth and yield of plants due to the decreasing water content and changes in some of the physiological and metabolic characteristics. ROS can cause oxidative stress and lipid peroxidation (membrane damage), destruction of proteins and photosynthetic pigment, the disruption of RNA and DNA functions, and result in serious damage to the cells and structures of the plants. As a result, it may reduce the leaf area of the plant which affects the root and shoot growth of the plant in turn [2]
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