The Lm1 line carrying genotype Lm1 +/+ y1-/- (lemon aleurone and white endosperm) was crossed with a 2-9m line (genotype Lm1 -/- y1-/-). The self-pollinated F3 ears were produced on 149 F2 plants. On 14 F3 ears all the grains were violet due to the genotype of the mother plant (C1+/+ R1+/+). The remaining 135 ears were divided into 4 classes: 1) 9 ears: all the grains are lemon; 2) 18 ears: the grains are lemon and white in a 3:1 proportion; 3) 50 ears: the grains are lemon and white, the proportion of lemon grains is 0.20-0.50; 4) 58 ears: all the grains are white. These numbers of classes correspond to a 1:2:6:7 ratio, and suggest digenic inheritance. So, we propose a second gene for lemon color (named Lm2 ). A positive allele originates from the Lm1 line, a negative one from the 2-9m line. The genotype of the mother F2 plant would be: Lm1 +/+ Lm2 +/+ for class 1; Lm1 +/- Lm2 +/+ for class 2; Lm1 +/+ Lm2 +/- and Lm1 +/- Lm2 +/- for class 3; Lm1 -/- Lm2~ and Lm1~ Lm2 -/- for class 4.
In class 3 the color intensity is highly variable, and classification is essentially more difficult than in class 2. Usually a relatively homogenous group of grains of maximal intensity (0.05-0.30 of total family volume) exists in class 3. This suggests that the action of the Lm2 gene essentially depends on gene dose: 1 dose provides no coloration, 2 doses provide slight coloration and only 3 doses provide maximal coloration.
The Lm2 locus remains unlocated.
Linkage with the loci of chromosomes 9 (sh1, wx1) and 10
(R1) was not detected.
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