Smut Gall Development in Adult Corn Plants Inoculated with Ustilago maydis. R. P. Thakur, Plant Pathologist, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics, Patancheru P.O., Andhra Pradesh 502324, India. K. J. Leonard, and J. K. Pataky. Research Plant Pathologist, USDA-ARS, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; and Assistant Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 73:921-925. Accepted for publication 28 April 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0921.

Tassel galls were induced in 100% of corn plants in which the leaf whorl was injected with a suspension of sporidia of compatible isolates of Ustilago maydis 3–10 days before tassel emergence. Ear galls were induced at high frequency in Tastyvee sweet corn plants in which the sporidial suspension was injected between the leaf sheath and stalk at the sixth, seventh, and eighth nodes below the top of the plant 0–8 days before tassel emergence. Gall development was more variable in stalks and axillary buds than in ears. Mean incubation periods for appearance of galls in sweet corn hybrids grown in pots, greenhouse soil beds, and field plots were 17.5, 16, and 19 days, respectively. Ear galls were much larger on plants inoculated in the field than on those inoculated in the greenhouse, but the size of galls on stalks or axillary buds did not differ significantly for greenhouse- and field-grown plants. Inoculated hybrids in soil beds in the greenhouse had 27–77% fewer ears than the same hybrids left untreated or injected with water; 25% of those with galls on primary or secondary ears produced at least one normal ear, 23% of those without ear galls but with galls on stalks or axillary buds produced ears, and 32% of those with galls only on leaves or tassels produced ears. The injection technique is suitable for studies of host-pathogen interactions between corn and U. maydis in which typical gall development for adult plants is essential, but it may require some refinement before it can be used to screen corn genotypes for quantitative resistance to common smut.