A Rapid and Efficient Method for Assessing Pathogenicity of <em>Ustilago maydis</em> on Maize and Teosinte Lines

Abstract

Maize is a major cereal crop worldwide. However, susceptibility to biotrophic pathogens is the primary constraint to increasing productivity. U. maydis is a biotrophic fungal pathogen and the causal agent of corn smut on maize. This disease is responsible for significant yield losses of approximately $1.0 billion annually in the U.S.1 Several methods including crop rotation, fungicide application and seed treatments are currently used to control corn smut 2 . However, host resistance is the only practical method for managing corn smut. Identification of crop plants including maize, wheat, and rice that are resistant to various biotrophic pathogens has significantly decreased yield losses annually [3][4][5] . Therefore, the use of a pathogen inoculation method that efficiently and reproducibly delivers the pathogen in between the plant leaves, would facilitate the rapid identification of maize lines that are resistant to U. maydis. As, a first step toward indentifying maize lines that are resistant to U. maydis, a needle injection inoculation method and a resistance reaction screening method was utilized to inoculate maize, teosinte, and maize x teosinte introgression lines with a U. maydis strain and to select resistant plants.Maize, teosinte and maize x teosinte introgression lines, consisting of about 700 plants, were planted, inoculated with a strain of U. maydis, and screened for resistance. The inoculation and screening methods successfully identified three teosinte lines resistant to U. maydis. Here a detailed needle injection inoculation and resistance reaction screening protocol for maize, teosinte, and maize x teosinte introgression lines is presented. This study demonstrates that needle injection inoculation is an invaluable tool in agriculture that can efficiently deliver U. maydis in between the plant leaves and has provided plant lines that are resistant to U. maydis that can now be combined and tested in breeding programs for improved disease resistance. Video LinkThe video component of this article can be found at

Fungal Pathogens of Maize Gaining Free Passage Along the Silk Road

“…Ustilago maydis , also known as Ustilago zeae and Ustilago zeae mays , is a biotrophic fungus that causes Corn Smut (Common Smut, Boil Smut) [58] (Table 1). It can enter the plant at various sites, including silks which results in large fungal growths (galls) on the ear [58,59,60].…”

“…Ustilago maydis , also known as Ustilago zeae and Ustilago zeae mays , is a biotrophic fungus that causes Corn Smut (Common Smut, Boil Smut) [58] (Table 1). It can enter the plant at various sites, including silks which results in large fungal growths (galls) on the ear [58,59,60]. However, infection by U. maydis is not exclusively viewed in a negative light by local peoples; Huitlacoche or “maize mushrooms” are ear galls caused by Corn Smut which are eaten as a delicacy in Mexico, Central America, and the United States [59,60].…”

Wild Relatives of Maize, Rice, Cotton, and Soybean: Treasure Troves for Tolerance to Biotic and Abiotic Stresses

“…Using these approaches Lennon et al was able to identify the teosinte-derived GLS resistance QTL located in bin 4.07. Teosinte was also reported to manifest resistance to corn smut disease (Chavan and Smith, 2014 ). Using genomic in situ hybridization technology, Wei et al ( 2001 ) identified the chromosomal locations of the Z. diploperennis- derived segments in maize × Z. diploperennis crosses that carried loci resistant to fungal diseases including northern corn leaf blight, southern corn leaf blight, and corn leaf spot diseases.…”

Monitoring of the enzymatic activity of intracellular lipases of <em>Ustilago maydis</em> expressed during the growth under nitrogen limitation and its correlation in lipolytic reactions

“…maydis is a basidiomycete that belongs to the Ustilagenaceae family, which is composed of fungi that are related to the infection of several types of crops. It is studied because of its biotechnological potential for producing value added compounds such as organic acids, enzymes, lipids, and biosurfactants, among others, with applications in the pharmaceutical, cosmetic, and food industries (Chavan and Smith, 2014;Paulino et al, 2017). As a biotrophic organism, U. maydis requires the plant to continue its growth, transiting between two forms during its cell cycle, a yeast-like saprophytic phase and a filamentous phytopathogenic phase (Chavan and Smith, 2014).…”