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This article in CS

  1. Vol. 17 No. 1, p. 126-132
    Received: May 18, 1976

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Characterization and Inheritance of a Spotted Leaf Trait in Alfalfa1

  1. M. R. Azizi and
  2. D. K. Barnes2



Few genetic markers are available in alfalfa (Medicago sativa L.) that do not reduce plant growth. A vigorous plant with spotted leaves was found in the ‘San Isidro’ variety. Spotted-leaf plants were characterized by newly formed leaves that appeared normal but developed chlorotic spots within one week. Effects of two temperatures( 17 and 30 C) and three photoperiods (12- 16-, and2 4-hours) on the leaf-spot trait were studied in both greenhouse and growth chambers. At 17 C the trait was readily expressed, but at 30 C no spotting occurred. Leaves developed at 30 C did not become spotted when subsequently exposed to 17 C. Conversely, spotted leaves that developed at 17 C did not show repair when exposed to 30 C. The development of spots was greatest with a 24-hour light period. Cytological studies showed that palisade cells and a few spongy misspell cells of the spotted-leaf tissue were deformed and deteriorated. The epidermal cells remained in tact.

Genetic studies conducted at 17 C with a 24-hour footprint dicated that the spotted-leaf trait was controlled by two tetrasomic genes with random chromosome inheritance. The SA— sbsbsbsb, SA— SB and sasasasa sbsbsb genotypes produced normal plants. The sasasasa SBSB— genotypes produced spotted-leaf plants. Incomplete penetrance in sasasasa SBsbsbsb plants produced about 20% spotted-leaf plants. It was hypothesized that severity of spotting was controlled by modifying genes and was not closely associated with the dosage of the SB allele. The spotted-leaf trait was not maternally inherited.

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