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Fungus may help rice thrive in warmer climate (and feed people)

July 14, 2011

While humanity may fail to take the necessary actions to curb global warming, there is some hope that the world’s masses may not necessarily starve to death. U.S. Geological Survey researchers based in Seattle have found fungi that grow symbiotically in the roots of salt-tolerant coastal dunegrass can confer the same salt resistance to rice plants. Furthermore these symbiotic fungi, called endophytes, can also give rice greater resistance to other stresses such as heat, cold and droughts.

In this study (published with free access to the public on PloSONE), the USGS researchers used three types of fungi to test their ability to develop within rice plants and confer resistance to stresses. SaltSym (Fusarium culmorum) is usually found growing in coastal dunegrass and allows the plants to grow in a gradient of salt concentrations, while TempSym1 and TempSym2 (both strains of Curvularia protuberata) are found in geothermal soil and confer resistance to high and low temperatures respectively. All three also give plants resistance to drought conditions. The researchers grew rice plants with and without these fungi and in the presence and absence of temperature and salt stresses.

They found that the fungi were able to improve the growth and crop yield of the rice plants  in the absence of stresses, and in the presence of the stresses the rice plants with fungi were able to thrive compared to the plants lacking fungi. The fungi themselves can survive in plants under normal conditions lacking their respective stresses; however they did not remain colonized in all of the plants by the end of the researchers’ experiments. In the presence of the stresses, fungi remained colonized in all of the plants throughout the same time period. Additionally, plants that were colonized with these fungi were able to reduce their water consumption, a key trait for survival droughts that plague some areas now and will affect others in the years to come.

Already many regions around the world are suffering from the challenges that droughts bring to agriculture as a result of global warming. Rising temperatures also place an enormous stress on plants, and the researchers note in their paper that warmer minimum air temperatures during growing seasons over the past few decades have caused rice yields in China and the Philippines to decrease substantially, with the trend expected to continue. It is difficult to say where evolution or genetic engineering will produce crop varieties that can thrive in these tougher conditions, but the fungi provide a new tool for farmers to use to adapt and improve their yields.

Furthermore, salt tolerance can be of substantial help for crops that grow in areas prone to flooding by saltwater. The researchers cite natural disasters such as the Indonesian earthquake and the subsequent tsunami in 2004, as well as a tidal surge that flooded southern Burma after a 2008 cyclone; these resulted in the inundation of rice fields, damaging crops and trashing yields. Thus these fungi can also address more localized issues in agriculture that can help soften the blows natural disasters bring to human populations.

While improving rice yields will have a substantial impact on agriculture’s ability to feed humans worldwide, other plants too may be able to benefit from this finding. Previous studies cited in the researchers’ paper demonstrated that these fungi were also able to colonize in a certain species of tomato, producing the same results. With the possibility that these fungi can have the same impact across many plants of different genetic makeups, there may very well be a glimmer of hope for the immense challenge that feeding humans around the world presents now and will likely more difficult in the future.

—Ian Yu, Science & Technology Editor

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