Effects of phosphate solubilization and phytohormone production of Trichoderma asperellum Q1 on promoting cucumber growth under salt stress

Salinity is one of the major abiotic stresses limiting crop growth and yield. This study investigated the underlying mechanisms of Trichoderma asperellum Q1 in promoting cucumber growth under salt stress, including the abilities of the strain to solubilize phosphate and to produce phytohormone. The results showed that T. asperellum Q1 could solubilize inorganic or organic phosphate and the activities of phosphatases and phytase could be detected in the culture supernatant. In hydroponic experiments, the growth of cucumber seedlings was increased in the hydroponic system treated by culture filtrate of strain Q1 with tricalcium phosphate or calcium phytate under salt stress. This strain also exhibited the ability to produce indole acetic acid (IAA), gibberellic acid (GA) and abscisic acid (ABA) in liquid medium without any inducers. The levels of those three phytohormones in cucumber seedling leaves also increased after inoculated with this strain, along with increased root growth and root activities of the plant. These results demonstrated the mechanisms of T. asperellum Q1 in alleviating the suppression effect of salt stress involving the change of phytohormone levels in cucumber plant and its ability of phosphate solubilization.