Monash University, Clayton, Victoria
Over one billion people eat cassava every day (primarily the tuberous roots). Below ground storage organs are an important component of global food security but are likely to respond differently to climate change relative to other crops. Rising sea levels are threatening agricultural production in coastal regions due to inundation and contamination of groundwater. The development of more salt tolerant crops is essential. Cassava is an important staple, particularly among poor subsistence farmers. Its tolerance to drought and elevated temperatures make it highly suitable for meeting global food demands in the face of climate change, but its ability to tolerate salt is unknown. Cassava stores nitrogen in the form of cyanogenic glucosides and can cause cyanide poisoning unless correctly processed. Previous research demonstrated that cyanide levels are higher in droughted plants, possibly as a mechanism for increasing resilience to oxidative stress. We determined the tolerance of cassava to salt at two different stages of development, and tested the hypothesis that cyanide toxicity would be higher in salt-stressed plants. Cassava was grown at a range of concentrations of sodium chloride (NaCl) in young plants (around tuber initiation) and older plants (during tuber expansion). Established plants were able to tolerate higher levels of salt stress to younger plants. Plants were only able to exclude sodium at relatively low concentrations. Foliar cyanogenic glucoside concentration increased under moderate salinity stress, possibly as a mechanism for tolerating stress but little change was observed in the tubers. We propose that the mechanisms for salinity tolerance are age dependent, and that this can be traced to the relative cost of leaves in young and old plants.