Arbuscular mycorrhizal fungi induced different proline accumulations in two sorghum accessions in a response to drought stress

Sorghum has good adaptability to drought stress conditions, but its early vegetative phase and the generative phase are susceptible to stress. Understanding the physiological response of plants under drought and mechanisms regulating drought tolerance in a plant, mediated by arbuscular mycorrhizal fungi (AMF) will be useful in developing a strategy to deal with drought. Here, a pot experiment was used to explore the growth performance, biomass production and physiological responses of two sorghum accessions (4183A and JP-1) inoculated by the AMF under drought stress, as well as the effect of AMF on soil enzyme and microbial stability. Based on growth observations, the AMF inoculation treatment had not significant effect on increasing the drought resistance of the two sorghum accessions. Drought stress decreased the rate of height increment for 4183A, and JP-1 accessions by 37% and 55%, respectively, compared to normal conditions. Shoot dry weight and root dry weight losses were up to 59% and 66%, respectively, compared to well-watered conditions. However, the interaction of AMF and plants to deal with drought can be captured through physiological response, particularly proline accumulation. AMF inoculation in JP-1 accession reduced proline accumulation (99.91 mM/leaf fresh weight) compared to non-AMF inoculated plants (149.86 mM/leaf fresh weight). It can be implied that mycorrhiza can reduce plant stress. In contrast to accession 4183A, there was an increase in the accumulation of proline in plants inoculated with mycorrhiza under drought conditions. Additionally, AMF inoculation improved acid phosphatase activity in the soil and proved crucial for maintaining the stability of the rhizosphere microorganisms under drought-stressed conditions.