Chromosome 6 satellite location of a high chlorophyll fluorescence mutation (hcf*-26)

Last year we reported (MGCNL 53) that a mutant (hcf*-26) blocked in light reaction photosynthesis was beyond the middle chromomere of the satellite and could be located in the distal chromomere. The mutant hcf*-26 possesses a yellow-green phenotype and had been reported to be uncovered by TB-6Sa (Leto and Miles, MGCNL 51:57-59). In order to more precisely cytogenetically locate hcf*-26, we crossed heterozygous satellite-interchanges as the female parent with heterozygous hcf*-26 plants as male parent. Under our greenhouse sandbench conditions, seed from self-pollinations of the heterozygous hcf*-26 plants resulted in green and near-luteus seedlings. None of the crosses between the heterozygous interchanges as female and heterozygous hcf*-26 as male yielded near-luteus seedlings when the satellite breakpoint was distal to the breakpoint of interchange T4-6(5227), which is located between the middle and distal chromomeres. Our results indicate that hcf*-26 is located between the breakpoint of T4-6(5227) and the proximal end of the distal chromomere marked by T3-6b. Thus, hcf*-26 is either between the middle and distal chromomeres or in the proximal portion of the distal chromomere. The breakpoint of T5-6(8219) has not been localized cytologically within the satellite; the lack of near-luteus seedlings in testcrosses of heterozygous T5-6(8219) and heterozygous hcf*-26 plants suggests that the breakpoint is in the distal chromomere.

Table 1. Tests to cytogenetically locate hcf-26. Smaller seed and a portion of remaining seed from crosses of heterozygous interchanges as female parent with heterozygous hcf-26 plants were planted. Data were collected from seed produced during the summers of 1978 and 1979.
      Smaller seed2 Remnant seed
Interchange Satellite1 break pt. Number of crosses Green Chlorophyll deficient Green  Chlorophyll deficient
3-6b proximal end of distal chromomere 4 144 0 259 0
2-6(001-15) distal end of distal chromomere 3 162 0 273 0
6-7(7036) distal end of distal chromomere 6 115 0 325 0
5-6(8219) "satellite" 2 34 0 70 0

1The satellite is comprised of 3 chromomeres in these strains.

2Smaller seeds are expected to include Dp-Df heterozygotes.

R. L. Phillips and S. A. Thompson

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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