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Genetics

Quantitatively Inherited Reactions of Alfalfa to Peronospora trifoliorum. D. Z. Skinner, Research assistant, Department of Plant Pathology, Kansas State University, Manhattan 66506; D. L. Stuteville, professor, Department of Plant Pathology, Kansas State University, Manhattan 66506. Phytopathology 75:717-721. Accepted for publication 7 February 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-717.

Infection-type (IT) data were obtained by inoculating plant populations derived from all possible self- and cross-pollinations, and some F₂ populations, of six diploid clones of Medicago sativa with three monoconidial isolates (I-5, I-7, and I-8) of Peronospora trifoliorum. Host effect on intensity of conidial production appeared to be inherited quantitatively. Analyses of variance indicated that primarily additive effects were involved in response to isolate I-8, while additive and nonadditive effects were involved in response to isolates I-5 and I-7. Comparisons of variances and covariances in IT data indicated that genes conditioning a reduced IT usually were dominant. In some cases, however, genes that conditioned a higher IT were expressed although genes that conditioned a reduced IT were present, which suggested epistasis.