Learning from wild Vigna: how should we develop a salt-tolerant crop?

Salt tolerance has been an important issue in agriculture. Many genes involved in salt stress have been identified, but this knowledge has not led to development of a salt-tolerant crop that are practically useful. Despite hundreds of transgenic plants have been tested, there are few examples that demonstrated yield performance that are practically applicable to salt-affected fields. It is therefore important to figure out which genes should be targeted for artificial manipulation. However, given there are >500 of genes involved, it is almost impossible to test all the possible combinations of genes and expression profiles even in model plants. In contrast, wild plants inhabiting coastal environments have acquired salt tolerance, often by enhancing the mechanisms that are also conserved in model plants. Elucidating the mechanisms and underlying genes in such wild plants should provide a clear guidance to the combinations of appropriate genes. The genus Vigna represents such wild plants because of its great diversity. Recent studies have revealed that multiple Vigna species have independently evolved salt tolerance in various ways. Some of the species are studied in detail, highlighting the significance of combining and pyramiding multiple mechanisms for improving salt tolerance of a plant.