2019 ASHS Annual Conference

Tomato (Solanum lycopersicum) is the world’s second most important vegetable crop in terms of per capita consumption. Currently global productivity of tomato is challenged by different environmental stresses especially drought due to inadequate irrigation and erratic rainfall. In recent years, naturally occurring beneficial soil microorganisms are receiving increased attention as a sustainable tool for improving crop production and inducing stress tolerance in both research and commercial production. The fungal genus Trichoderma exists ubiquitously in soils worldwide and members of this genus are well-known to colonize plant root forming symbiotic relationships that promote plant growth, especially under adverse environmental conditions (e.g., drought, salt stress, nutrient deficiency). But the efficacy of colonization can be isolate specific, and the beneficial effect of Trichoderma may depend on the specific plant genotype. Therefore, the overarching goal of this project is to examine the potentiality of Trichoderma isolates, primarily native to Nepal, to ameliorate drought stress in tomato. Forty-one Trichoderma isolates were collected from various agroecological regions of Nepal (i.e., wet to dry). In addition, two Trichoderma isolates from Ohio and a commercially available form of Trichoderma harzianum-TH22 were selected for this study. An in-vitro assay was undertaken to identify Trichoderma isolates with potential to survive in low moisture environments. Only fourteen isolates were selected as desiccation tolerant as they were able to grow at low moisture content of -8.5 Matric potential induced by polyethylene glycol 8000 in Potato Dextrose Agar plates. Twenty-four isolates were further tested for tomato growth promotion and drought tolerance capacity under greenhouse conditions. Under irrigation, twelve isolates resulted in greater plant biomass, compared to the non-inoculated control. Furthermore, a subset of isolates resulted in greater tomato performance under drought. Out of 24 Trichoderma studied, five (T3, T-16, T-31, T33, T37, T43, T44) showed lower wilting symptoms under drought and recovered faster after irrigation. In addition, tomato plants treated with isolates T16, T31, T33, T37 had 25-30 % more shoot biomass as compared to control under the drought stress condition. Isolates T16, T31, T33, T37 were originally collected from the drier areas of Nepal and were capable to promote growth under drought stress, as compared to those collected from wet areas, indicating a potential adaptation to this extreme condition.