Genetic variation in meiotic behaviour and fertility in tetraploid Hyoscyamus muticus: correlation with diploid meiosis

Abstract

Autotetraploidy was induced in 19 morphologically distinct genotypes of the medicinal solanaceous plant Hyoscyamus muticus (Egyptian henbane, 4x= 56). The multivalent association frequencies at metaphase I of meiosis ranged from 0.328 to 0.628 and were positively correlated with the chiasmate association frequency in the diploid progenitors. The frequent absence of chiasmata in one of the two chromosome arms in most of the tetraploids was attributed to interference between the arms and to pairing partner exchange in one of the chromosome arms instead of around the centromers. The bivalent frequency in the tetraploids was positively correlated with pollen fertility and seed set. The latter ranged from 7.5 to 68.5 per cent. The asymmetry of the karyotype was not reflected in the distribution of open bivalents in the diploid. The regression coefficients of metaphase I chromosome associations over fertility in the tetraploid suggested that, in the range covered, one multivalent less resulted in an increase of about 12 per cent in seed set. The regression of open bivalent frequency in the diploid progenitor over seed set in the tetraploid suggested that one open bivalent more in the diploid would result in almost 18 per cent seed set in the tetraploid. It is concluded that the selection of diploid progenitors with high frequencies of open bivalents should enhance the fertility of the artificial polyploids in H. muticus.