Corn-Smut Disease: Profit Potential and Nutritious!

Corn-Smut Disease picture of diseased ear

Corn-Smut Disease

Corn-Smut Disease.

Corn-smut is a disease caused by the fungus, Ustilago maydis. In this disease, the fungal spores enter through the corn silks  (Note: each silk represents a single kernel created when the corn silk is pollinated). Once pollination is completed and the silks appear darkened brown; the silks do not distinguish between a pollen grain and a fungal spore–it simply appears as if pollination has taken place. At this point, the infection has already begun.

The fungus takes over the genetic machinery and redirects it to produce spore-filled kernels. The spores can be seen as a black grainy dusty substance released when the sac breaks apart; the white membrane from one galls  cracked open and revealed the spore mass (see top left of photo). Most new hybrid corn varieties are resistant to corn-smut disease. The heirloom varieties, however, can be quite susceptible. We have not seen this disease in our garden since we started using newer varieties of sweet corn. This year, however, we decided to try an heirloom in the Spring garden (several attempts to grow sweet corn were thwarted by the late frosts—this heirloom was the 3rd set of corn seed to be planted.) Infected kernels of corn are replaced by membrane-bound galls of black spores. So far, we found 2 infected ears out of about 200 in the garden.

 Some Interesting Facts about Corn-Smut Pathogen.

Ustilago maydis is a plant pathogen that can create a desirable disease that benefits humans in both economic profit potential and known nutritional value! In Mexico, this fungus is a delicacy that is eaten–often as a filling in tacos and quesadillas. The nutritional value of the corn is improved by this fungus and it the profit margin can be higher (depending on farm size) for raising smut-infected corn as compared to healthy corn. The spores are higher in proteins and rich with the amino acid, Lysine—not naturally produced in corn!

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