VIEW ARTICLE

Genetics

Association of Rmd1, a Gene Conditioning Reaction to Maize Dwarf Mosaic Virus, with Genes Conditioning Endosperm Color (y1) and Type (su2) in Maize. C. W. Roane, Professor emeritus, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061; S. A. Tolin(2), H. S. Aycock(3), and P. J. Donahue(4). (2)Professor of plant pathology, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061; (3)Former assistant professor, Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, Present address: 5776 Vesper Drive, South Beloit, IL 61080; (4)Research associate of agronomy, Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061. Phytopathology 79:1368-1372. Accepted for publication 30 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1368.

Factors in maize conditioning resistance to maize dwarf mosaic virus (MDMV) have been shown by others to occur on chromosome 6. Genes conditioning endosperm color (y1) and type (su2) also occur on chromosome 6. Therefore, maize inbred lines B68, Oh7B, and Pa405 having Rmd1, and Va85 probably having Rmd1, a gene conditioning resistance to MDMV strain A (MDMV-A), were crossed to the genetic marker stock Ill76, having the y1 and su2 genes and which is susceptible to MDMV. The crosses were assumed to be of the genotype Rmd1 Rmd1 Y1 Y1 Su2Su2 × rmd1rmd1y1y1su2su2. All characters are monogenic and completely dominant; thus, a 3:1 ratio was expected for each character in the F₂. The expected ratios were not achieved; therefore, the data were analyzed by calculating chi-square values for pairs of characters from contingency tables. For the B68, Oh7B, and Pa405 crosses, chi squares for MDMV reaction and endosperm color (rmd1/y1) were the largest, indicating closest association of gene loci. Chi squares for reaction and endosperm type (rmd1/su2), were the smallest, indicating least association of loci. The chi squares for endosperm color and type (y1/su2) were intermediate. Thus, rmd1 is near the y1 locus and on the centromere side of it, since it is a greater distance from su2 than is y1. The cross Va85 × Ill76 produced results inconsistent with the other crosses.