Downy mildew is a serious threat to corn (maize) production in the tropics and subtropics. Corn is native to Central America, and was introduced into South-East Asia by the Spanish colonisers in the 1700s. Corn is evolutionarily naïve to downy mildews of the genus Peronosclerospora . Consequently, corn monocultures are particularly susceptible to a variety of Peronosclerospora species, which spread to the crop from local grass...