ORIGINAL PAPER Biocontrol Potential of Salt-Tolerant Trichoderma and Hypocrea Isolates for the Management of Tomato Root Rot Under Saline Environment Prem Lal Kashyap 1,2 & Manoj Kumar Solanki 2,3 & Prity Kushwaha 2 & Sudheer Kumar 1 & Alok Kumar Srivastava 2 Received: 24 May 2019 /Accepted: 1 October 2019 # Sociedad Chilena de la Ciencia del Suelo 2019 Abstract The aim of present study was to decipher the effect of salinity stress on growth and antagonistic potential of Trichoderma and Hypocrea isolates against tomato root rot pathogen (Rhizoctonia solani AG-4) under saline soil conditions. In vitro salinity assays, dual plate confrontation, and volatile metabolite assays were employed to establish the antagonistic potential of Trichoderma and Hypocrea isolates against R. solani AG-4 under varied salt gradients. Potential Trichoderma and Hypocrea isolates were evaluated against tomato root rot disease in greenhouse conditions under salt stress condition. Polymerase chain reaction (PCR) assay was performed to confirm the presence of endochitinase gene in salt-tolerant antagonists. Enzyme and biochemical assays were conducted to define the role of compatible solutes and defense-related enzymes in controlling tomato root rot under saline soil conditions. Trichoderma and Hypocrea isolates were capable to grow and sporulate up to 250 mM NaCl and also showed strong antagonism against R. solani. Enzymatic estimation of hydrolytic enzymes and amplification of endochitinase gene suggested that the test isolates are potent antagonistic agents. Under greenhouse evaluation, Trichoderma and Hypocrea fortified tomato plants showed significant reduction in tomato root rot disease in saline soils over untreated control. Significant increase in total phenol, polyphenol oxidase, peroxidase, β-1,3-glucanase, phenylalanine lyase, chitinase, proline, reducing sugar, and total soluble sugar displayed direct association with salt stress tolerance. Application of salt-tolerant Trichoderma and Hypocrea isolates emerged as a simple, safe, and cheap method for the biological management of tomato root rot under saline condition. Keywords Biological control . Rhizoctonia solani . Root rot . Salinity . Trichoderma 1 Introduction Salt stress is recognized as one of the major constraint factors for sustainable crop growth and production. Salinity stress leads to a series of morphological, physiological, biochemical, and molecular alterations that affect all the key processes of agriculture crops such as germination, growth, photosynthe- sis, water relation, nutrient imbalance, oxidative stress, and yield (Yasin et al. 2018; Wang et al. 2003). Mechanistically, salt stress causes ion imbalance and trigger ion toxicity- induced disturbances in plant metabolism (Kushwaha et al. 2019; Parihar et al. 2015). As a result, enhanced production of reactive oxygen species (ROS) induces oxidative injury of membranes, proteins, lipids, DNA, and chlorophyll (Bai et al. 2018). Besides this, elevated sodium contents in plant tissues also obstruct phosphorylating and non-phosphorylating elec- tron transport pathways in combination with reduced respira- tory and photosynthetic activity (Jacoby et al. 2016). To pre- vent this damage to cellular components by ROS, plants have developed an enzymatic (e.g., catalase, glutathione reductase, and peroxidases) and non-enzymatic (ascorbate, carotenoids, flavonoids and other phenolic compounds, etc.) detoxification systems (Taïbi et al. 2016; Aghaei et al. 2009). Furthermore, plants accumulate soluble sugars and proline to tolerate salt * Prem Lal Kashyap plkashyap@gmail.com 1 ICAR-Indian Institute of Wheat and Barley Research (IIWBR), Karnal 132001, India 2 ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Mau, Uttar Pradesh 275103, India 3 Present address: Department of Food Quality & Safety, Institute for Post-harvest and Food Sciences, The Volcani Center, Agricultural Research Organization, Maccabi Road 68, P.O.B 15159, Rishon LeZion 7528809, Israel Journal of Soil Science and Plant Nutrition https://doi.org/10.1007/s42729-019-00114-y