Bioprospecting Drought Tolerant Trichoderma harzianum Isolates Promote Growth and Delay the Onset of Drought Responses in Wheat (Triticum aestivum L.)

The objectives of this study were to investigate whether seed biopriming through drought tolerant isolates of Trichoderma harzianum induces drought tolerance in wheat. Physiological and biochemical parameters were also monitored under greenhouse conditions to explore the mechanism underlying plant water stress resilience in response to Trichoderma inoculation.The impact of bioprospecting Trichoderma harzianum drought tolerant isolates, Rani Th-14, Rani Th-21, Rani Th-25, Rani Th-30 and Rani Th-39 on wheat response to drought was studied. Measurements of the stomatal conductance, net photosynthesis, chlorophyll fluorescence and greenness of plants were performed. In addition, analysis of the total phenolic compounds, free proline, MSI (membrane stability index) as well as lipid peroxidation was carried out. With or without exposure to drought conditions, colonization by Trichoderma isolates promoted seedling growth, the most consistent effect being an increase in shoot and root growth. The primary direct effect of colonization was promotion of root growth, regardless of water status, and an increase in water content, which it is proposed, caused a delay in many aspects of the drought response of wheat. Colonization of Trichoderma by seed biopriming enhanced drought tolerance of wheat plants as they delayed drought induced changes like stomatal conductance, net photosynthesis, chlorophyll fluorescence and greenness of plants. Drought stress from 4 to 13 d of withholding water induced an increase in the concentration of many stress induced metabolites in wheat leaves, while Trichoderma colonization caused a decrease in proline, MDA and H 2 O 2 contents and an increase in phenolics concentration. Among different Trichoderma isolates, Rani Th-14 induced maximum drought tolerance as treated plants recorded only 20-40 per cent wilting even at 13 days drought stress (DDS). The study is important as the experiments confirmed that the drought tolerant isolates of Trichoderma through seed bio priming are critical in inducing tolerance to drought.