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Histopathology of Resistance in the Sorghum bicolor-Sphacelotheca reiliana Interaction. J. M. Wilson, Former Graduate Research Assistant, now Plant Breeder, Asgrow Seed Company, San Antonio, Texas 78211; R. A. Frederiksen, Associate Professor, Department of Plant Sciences, Texas A&M University, College Station 77843. Phytopathology 60:1365-1367. Accepted for publication 6 April 1970. DOI: 10.1094/Phyto-60-1365.

Hypodermic inoculation of five resistant sorghums with compatible monosporidial lines of S. reiliana resulted in three different host-parasite interactions. Early Hegari and F1's having Early Hegari as the male parent were compatible with the pathogen for several days before becoming incompatible. The length of time before the host-parasite relationship became incompatible varied with incubation temp and the genotype of the female parent. The incompatible reaction was characterized by the disappearance of mycelium and the appearance of teliosporelike objects in the host. Lahoma Sudangrass, White Kafir P.I. 48770, and kafir B65L-5427-3 had similar reactions to the monosporidial inoculum. In each entry, hyphal growth or sporidial germ tubes were present in the inoculation wound, but the pathogen did not grow into the host tissue. The reactions were not altered by different temp. Feterita Tx09 and F1's involving this entry were characterized by the complete inhibition of sporidial development and fusion. This reaction was also stable over a range of temp. A "squash" technique was developed to rapidly identify reaction type.