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Crop Science Abstract -

Inheritance of Resistance to Phytophthora megasperma in Diploid Alfalfa1


This article in CS

  1. Vol. 21 No. 2, p. 271-276
    Received: Mar 10, 1980

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  1. J. A. G. Irwin,
  2. D. P. Maxwell and
  3. E. T. Bingham2



Few genetic studies have been made to determine the inheritance of disease resistance in diploid alfalfa (Medicago saliva L.). The objectives of this study were to determine the inheritance of resistance to Phytophthora root rot in Wisconsin cultivated diploid alfalfa (CADL) and in diploid Medicago coerulea Less. (PI 299046).

S1 populations and F1 populations from crosses of resistant and susceptible plants of CADL were generated, and their segregations for disease reaction indicated that resistance was conditioned by two dominant complementary genes, designated Pm1 and Pm2. The observed segregations in S2 F2 testcross families of CADL provided additional evidence to support this model. Segregations for resistance to Phytophthora root rot in S1, F1 and F2 families from intercrosses of two resistant Medicago coerulea plants and two susceptible CADL plants indicated that resistance in M. coerulea was complex, and that epistatic relationships might be of importance.

These studies indicate the potential usefulness of diploid alfalfa as new sources of resistance to Phytophthora root rot.

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