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Inheritance of Resistance to Maize Dwarf Mosaic Virus in Maize Inbred Line Oh7B. C. W. Roane, Professor, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; S. A. Tolin(2), and C. F. Genter(3). (2)(3)Associate professor of plant pathology, and professor emeritus of agronomy, respectively, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061. Phytopathology 73:845-850. Accepted for publication 23 November 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-845.

The inheritance of reaction to maize dwarf mosaic virus (MDMV) was studied in progenies derived from crosses between the resistant maize inbred line Oh7B and two susceptible lines, Oh43 and Pa91. Field-grown seedlings at one- to three-leaf stage were mechanically inoculated with a johnsongrass isolate of MDMV; no natural inoculum was present. Reactions of parental, F1, F2, and F3 plants at the postanthesis stage were scored on a scale of 1- 7. Scores of 1- 4 were considered resistant, and 6 and 7 were susceptible. Class 5 plants could be considered either resistant or susceptible, but from our analyses we concluded that they belong in the resistant class. The F3 progenies were from randomly selected, classified F2 plants. Three procedures were used to interpret genetic control of MDMV reactions: direct classification of F2 plants, determining F2 phenotypes from mean scores of F3 rows, and determining F2 genotypes from inspection of scores of individual F3 plants. The three methods gave similar segregation ratios. We conclude that reaction to MDMV in Oh7B is conditioned by one dominant gene.

Additional keywords: corn viruses, fate map, maize chlorotic dwarf virus, reaction classes.