RECOMBINATION RATE DIFFERENCES FOR POLLEN PARENTS AND SEED PARENTS INPINUS-PINASTER

Significantly less recombination was observed for the female gametes t han for the male gametes in one individual of maritime pine (Pinus pin aster Ait.). Two segregating mapping samples of the same hybrid tree w ere used for genomic mapping. One sample consisted of diploid tissues from 192 F-2 seedlings. The other sample consisted of megagametophytes (haploid maternally derived nutritive tissue) extracted from 156 germ inated F-2 seedlings. A total of 94 RAPD markers covering 65 per cent of the genome was used for constructing the maps with both samples. Co mparison for the total length of the two maps shows that meiotic tic r ecombination differs between the haploid and the diploid mapping sampl es. Map distances in the diploid mapping sample were on average 14 per cent larger than in the megagametophyte sample, corresponding to a 28 per cent greater rate of recombination in the pollen parent. Departur e from homogeneity of recombination rate was also tested by marker int erval using a likelihood-based method. Inference for greater meiotic r ecombination during male gametogenesis was verified analytically. A ge nome-wide reduction in the female gamete's recombination rate in gymno sperms presents interesting evolutionary implications, as this is exac tly the opposite trend to that in the angiosperms studied so far. Dire ct consequences for pine tree breeding are also discussed.