Effectiveness of Indigenous Arbuscular Mycorrhizal Fungi Inoculum in Enhancing Tolerance of Sorghum (Sorghum bicolor (L) Moench) to Water Stress

Abstract

Sorghum (Sorghum bicolour L. Moench) is an important cereal crop ranked second after maize as a staple food in Ethiopia. However, its production is threatened by low soil fertility and moisture content. Arbuscular mycorrhizal fungi (AMF) have shown their importance in nutrient and water uptake and mitigating drought stress resulting in better yields of crops. Hence, this study was initiated to investigate the effect of indigenous arbuscular mycorrhizal fungi to enhance growth of two selected sorghum varieties (Melkam and Local seed varieties) under drought conditions. AMF was propagated in trap culture. The experimental design was arranged in a randomized complete block design with three replications under greenhouse conditions. Four treatments were set up for sampling sites at Diredawa, Jigjiga and Harar field sites: sorghum with AMF inoculation at 80% soil field capacity (+AMF+80%FC), plants without inoculation of AMF (controls) at 80% soil field capacity (-AMF+80% FC), plants inoculation with AMF at 50% soil field capacity (+AMF+50%FC) and plants with AMF inoculation at 25% soil field capacity (+AMF+25%FC). Data of plant growth parameters on sorghum seedlings, and AMF colonization percentage and AMF diversity and spore density were collected. Analysis of variance (ANOVA) was used to analyze data using SPSS software package (version 26.0) and significant means separated using Tukey’s test at 5% significance level. In this study, the highest spore density and highest root colonization rate of AMF were recorded from trap culture of maize from Diredawa location. The result also showed that Melkam variety showed the highest shoot fresh and dry weights (14.73, 3.23g/plant, highest root fresh and dry weights (8.13, 2.16g/plant) and longest roots (39cm) at 80%FC. Relative water content, proline, total soluble sugar and total chlorophyll content were significantly (p <0.05) influenced by inoculation of AMF in both varieties at all soil water field capacity. A total of 24 AMF species belonging to 15 genera were detected from trap culture experimental soil of all locations. Gigaspora, Claroideoglomus, Funneliformis and Rhizophagus were the common genera detected in the trap culture. This study demonstrated that AMF inoculants had a good potential in improving sorghum growth under water stressed conditions. Such strategies could enable food production in marginal areas characterized by low rainfall and high temperatures. However, the application of present findings should be validated under field conditions.