Use of half - tetrad analysis to discriminate betweeIl two types of 2 n egg formation in a potato haploid
نویسنده
چکیده
r The ratio of the first division restitution (FDR) to second division restitution (SDR) 2n eggs was estimated in 4182t, a haploid (2n = 2x = 24) of Solanum tuberosum L. that produces 2n eggs by the two modes. The segregation of three genes previously mapped relative to their centromeres, Pgm-2 (2.0 cM), Mdh-1 (33.5 cM), and 6-Pgdh-3 (30.1 cM) was analyzed in the tetraploid offspring of a 2x x 4x cross. Based on the segregation of the Pgm-2 locus, 39.70/0 of the progeny originated from FDR 2n eggs and 60.30/0 from SDR. Segregation patterns of the two distal loci within the FDR-derived 4x subpopulation indicated that the gene-centromere recombination rate during megasporogenesis was significantly reduced for Mdh-1 when compared with a previous estimate during microsporogenesis. In the SDR derived 4x subpopulation, the gene-centromere recombination rates for Mdh-1 and 6-Pgdh-3 were not significantly different from previous estimates. Tetraploid progeny generated from one 2x x 4x cross where the 2x parent produces 2n gametes by two modes can be used to make an unbiased comparison of the potential breeding value of FDR and SDR gametes.
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