An effective in-vitro selection of water spinach (Ipomoea aquatica Forsk.) for NaCl-, KH2PO4- and temperature-stresses

Abstract

Inorganic substances found in wastewater (i.e. industrial, agricultural, and urban-sewage runoff) constitute a form of abiotic stresses for plants, negatively impacting their growth, development, and productivity. The aim of this investigation is to establish an effective in-vitro selection system, to identify water spinach varieties displaying higher tolerance to inorganic salts and evaluated temperature. High inorganic salt concentrations (171 mM NaCl or 125 mM KH2PO4 strongly retarded chlorophyll concentration and relative water content, led to growth reduction, and decreased the seedling survival percentage of a commercial variety of water spinach. The fresh weight, shoot height, and leaf number of seedlings grown under inorganic stresses were also strongly decreased when compared to unstressed control seedlings. Moreover, seedlings grown at high temperature (30 ± 2°C) exhibited 4-folds reduction in survival percentage compared to those grown at low temperature (10±2°C). An in-vitro selection system was then applied to screen 54 varieties of water spinach. The results indicated that 10 varieties processed increased tolerance to high inorganic salt levels and evaluated temperature. These tolerant varieties should be further investigated in filed trials for vegetable production, contaminant absorption, and wastewater treatment. Conversely, the sensitive varieties may potentially be used as indicators for pollutant contamination in wastewater.