Corn smut

Appearance

Although it can infect any part of the plant, it usually enters the ovaries and replaces the normal kernels of the cobs with large, distorted tumors analogous to mushrooms. These tumors, or "galls", are made up of much-enlarged cells of the infected plant, fungal threads, and blue-black spores The spores give the cob a burned, scorched appearance. The generic name ''Ustilago'' comes from the Latin word ''ustilare'' .

Naming

In Mexico, corn smut is known as ''huitlacoche'' . This word entered Spanish in Mexico from classical Nahuatl, though the Nahuatl words from which huitlacoche is derived is debated. In modern Nahuatl, the word for ''huitlacoche'' is ''cuitlacochin'' , and some sources deem ''cuitlacochi'' to be the classical form.

Some sources wrongly give the etymology as coming from the Nahuatl words ''cuitlatl'' [ˈkʷit͡ɬɑ] and ''cochi'' [ˈkot͡ʃt͡ɬi] , thus giving a combined mismeaning of "sleeping/hibernating excrement"., but actually meaning "sleeping excrescence", referring to the fact that the fungus grows in between the corns and impedes them from developing, thus they remain "sleeping".

A second group of sources deem the word to mean "raven's excrement". These sources appear to be combining the word ''cuitlacoche'' for "thrasher" with ''cuitla'', meaning "excrement", actually meaning "excrescence". However, the avian meaning of ''cuitlacoche'' derives from the Nahuatl word "song" ''cuīcatl'' [ˈkʷiːkɑt͡ɬ], itself from the verb "to sing" ''cuīca'' [ˈkʷiːkɑ]. This root then clashes with this reconstruction's second claim that the segment ''cuitla-'' comes from ''cuitla'' .

One source derives the meaning as "corn excrescence", using ''cuītla'' again and "maize" ''tlaōlli'' [t͡ɬɑˈoːlːi]. This requires the linguistically unlikely evolution of ''tlaole'' "maize" into ''tlacoche''.

Behavior

When grown in the lab on very simple media, it behaves like baker's yeast, forming single cells called sporidia. These cells multiply by budding off daughter cells. When two compatible sporidia meet on the surface of the plant, they switch to a different mode of growth. First, they send out conjugation tubes to find each other, after which they fuse and make a hypha to enter the maize plant. Hyphae growing in the plant are dikaryotic; they possess two haploid nuclei per hyphal compartment. In contrast to sporidia, the dikaryotic phase of ''U. maydis'' requires infection of the plant to grow and differentiate, and cannot be maintained in the laboratory.

Proliferation of the fungus inside the plant leads to disease symptoms such as chlorosis, anthocyanin formation, reduced growth and the appearance of tumors harboring the developing teliospores.

Mature spores are released from the tumors and spread by rain and wind. Under appropriate conditions, a metabasidium is formed in which meiosis occurs. Resulting haploid nuclei migrate into elongated single cells. These cells detach from the metabasidium to become the sporidia, thus completing the life cycle.

Uses

:''See also: List of delicacies''
Smut feeds on the corn plant and decreases the yield. Smut-infected crops are often destroyed, although some farmers use them to prepare silage. The smut is a delicacy in Mexico, where it is known as ''huitlacoche'', even being preserved and sold for a significantly higher price than uninfected corn. The consumption of corn smut originates from Aztec cuisine. For culinary use, the galls are harvested while still immature — fully mature galls are dry and almost entirely spore-filled. The immature galls, gathered two to three weeks after an ear of corn is infected, still retain moisture and, when cooked, have a flavor described as mushroom-like, sweet, savory, woody, and earthy. Flavor compounds include sotolon and vanillin, as well as the sugar glucose.

The fungus has had difficulty entering into the American and European diets as most farmers see it as blight, despite attempts by government and high profile chefs to introduce it. In the mid-1990s, due to demand created by high-end restaurants, Pennsylvania and Florida farms were allowed by the United States Department of Agriculture to intentionally infect corn with ''huitlacoche''. Most observers consider the program to have had little impact, although the initiative is still in progress. The cursory show of interest is significant because the USDA has spent a considerable amount of time and money trying to eradicate corn smut in the United States. Moreover, in 1989, the James Beard Foundation held a high-profile ''huitlacoche'' dinner, prepared by Josefina Howard, chef at Rosa Mexicano restaurant. This dinner tried to get Americans to eat more of it by renaming it the Mexican truffle and it is often compared to truffles in food articles describing its taste and texture.

Native Americans of the American Southwest, including the Zuni people, have used corn smut in an attempt to induce labor. It has similar medicinal effects to ergot, but weaker, due to the presence of the chemical ustilagine.