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This article in CS

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


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doi:10.2135/cropsci1977.0011183X001700010034x

Characterization and Inheritance of a Spotted Leaf Trait in Alfalfa1

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

Abstract

Abstract

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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