Delicious, juicy tomatoes. (Source: Lars Blankers)
A tomato is a common sight in our everyday diets. Its smooth, bright red texture, and the explosion of tangy, sweet juice after you sink your teeth into it makes it a popular choice for any kind of food. From appetizers to even desserts, the tomato stands as an ingredient of high demand in countless culinary cultures all over the world.
Tomato farmers make up the large demand for tomatoes through advents of industrial agriculture; usage of vehicles to plow more land, powerful fertilizers to facilitate plant growth, etc. But one large obstacle that has hindered the production of these plants is the lack of freshwater. Since the supply of freshwater is so low, many farmers rely on light saltwater to irrigate their plants.
Saline waters can be used for crop irrigation and moreover have been used for millennia. But when growing these sumptuous fruits (or vegetables, depending on your perspective), salt in the soil or salty irrigation water can be detrimental. While not fatal to the survival of a tomato plant, salt water can have the effect of reducing the yield of the fruit which is critical for a fruit of such high demand.
In a recent paper in the journal PLOS One by researchers at Hohai University and Henan Agriculture University on the effects of saline water drip irrigation on tomato yield and quality, a three-year study on the effects of saline water irrigation was presented for different soil salt contents. Saline water differing in electrical conductivity (from 3 dS/m to 5.5 dS/m) was supplied to the plant after the seedling establishment. Irrigation water with 5.5 dS/m salinity reduced the maximum leaf area index and chlorophyll content most significantly when compared with other salinity treatments. Not only that, saline water decreased the yield by around 20 percent compared with the control, but improved tomato quality, including fruit density, soluble solid, total acid, vitamin C and the sugar-acid ratio.
Many efforts have been made to increase the salt tolerance of tomato plants so that they can preserve yield amount while also maintaining the benefits of saltwater irrigation. These efforts have come in many ways, such as incorporating genes that allow for the formation of a vacuole to pump sodium out of the plant faster. But perhaps one of the most interesting improvements come in the form of a unique fungi.
Piriformospora indica inside Coleus forskohlii. (Source: PLOS One)
Plant scientists at the Cairo University of Agriculture found out that adding a desert root fungus, Piriformospora indica, which was first isolated in India, to the soil in which the tomatoes are grown in protects the tomatoes from the damaging effects of high salinity. Tomatoes were planted in a greenhouse, half of which were placed in the fungi. Next, half of each group were fed freshwater and that the other half light saltwater. The leaves of the tomato plants within fungi made more sodium regulating enzymes by expressing the genes PIP1;2, PIP2;4, TIP1;1 and TIP2;2. What’s more, the plant was better able to maintain proper levels of potassium, which is necessary for growth, as stated by the researchers in the journal Scientia Horticulturae. But even more, the fungi increased fruit yield. For the plants irrigated with salty water, fungal infection of the roots boosted the yield of tomatoes 65% compared with uninfected plants. Even infected tomatoes irrigated with freshwater did better, with a 22% increase in yield.
As the human population continues to grow and freshwater supplies reduce, methods to increase the yields of agriculture become ever-more relevant. In the case of tomatoes, Piriformospora indica serves as an effective measure for ensuring a steady supply of tomatoes. However, perhaps a more important issue would be reducing the rate at which freshwater supplies are depleted and agricultural soil dried of moisture. Through a combination of regulations in agriculture and advancements in science, we can secure a much more sustainable tomato market.
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