Fungal endophytes that confer tolerance to salt and dry conditions
Azad, Kumkum 1985-
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Fungal endophytes grow symbiotically inside plants, where some strains promote plant growth and survival under particular abiotic stresses. Tomato (Solanum lycopersicum Var. Rutgers) seeds were inoculated with systemic (also called class 2) fungal endophytes (Alternaria spp and Trichoderma harzianum). These endophytes were isolated from plants naturally growing in salinized-soil in Saskatchewan, e.g. Little Manitou Lake shore, Radisson Lake shore, and Mosaic Belle Plaine tailings area. The effects of colonization with systemic fungal endophytes were studied on growth performance of tomato plants under NaCl and drought stress. Endophyte-colonized plants had greater fresh shoot biomass than control plants after 20 d of NaCl stress (300 and 500 mM). They also maintained greater fresh root biomass after 10 d NaCl stress (300 mM). After exposure to chronic 100 mM and 200 mM NaCl stress, there was no remarkable difference in plant biomass (both root and shoot) between endophyte-colonized plants and non-colonized control plants. Exposure to NaCl stress altered different aspects of the plants’ physiology such as photosynthetic efficiency, osmolyte adjustment, and reactive oxygen species generation. Photosynthetic efficiency was improved by endophyte colonization during chronic NaCl stress, but decreased significantly during ≥400 mM NaCl stress. Although osmolality of plants increased with the increase of NaCl salinity, there was no effect of endophyte colonization on plant osmolality. On the other hand, reactive oxygen species activity of endophyte-colonized plants was always lower in comparison to non-colonized control plants in response to NaCl stress. Endophyte-colonized plants growth performance and physiological responses were also determined under drought. Endophyte-colonized plants had significantly higher shoot biomass in comparison to non-colonized control plants after intermittent drought and continuous drought. Physiological responses of plants differed following intermittent and continuous drought stress. Photosynthetic efficiency of endophyte-colonized plants improved significantly after intermittent drought, but there was no effect of endophyte colonization on photosynthetic efficiency of plants after continuous drought. On the other hand, increased proline accumulation and decreased osmolyte concentration were observed in endophyte-colonized plants in response to drought stress. There was also indication of less reactive oxygen species in endophyte-colonized plants upon drought stress. Finally, better fluid use efficiency of endophyte-colonized plants was observed, which is correlated to drought tolerance in endophyte-colonized plants. These results suggest that our systemic fungal endophytes have the potential to improve agriculture and horticulture on salinized and dry soils which are common phenomenon in semi-arid environments.
DegreeMaster of Science (M.Sc.)
CommitteeKaminskyj, Susan; Basinger, Jim; Wilson, Ken; Knight, Diane
Copyright DateApril 2016