A study of 154 S1 lines of maize was made for the frequency of chlorophyll lethal genes. These lines showed a frequency of chlorophyll lethals between 3-25%. They were crossed with a line without chlorophyll lethals. The F1 plants did not show any chlorophyll lethals. The frequency of chlorophyll lethals in S1 and F2 of these crosses is shown in Figure 1. Forty-seven percent of the studied lines showed a tendency to increase frequency of chlorophyll lethals, 2% of them had the same frequencies for chlorophyll lethals, 20% showed a tendency to decrease the frequency of chlorophyll lethals, and 31% of the lines showed no chlorophyll lethals in F2. Study of these lines as females and males revealed low gametic transmission in both sexes.
This may indicate an effect on differential gametic viability, which would explain the deficit of the lethals in the heterozygous segregation (gametic drift). This may also suggest the presence of zygotic lethals, gametic lethals, and combinations thereof.
Figure 1: Frequency distributions of chlorophyll lethals, shown in percent of plants.
Juan C. Salerno
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