The genetics of distyly and homostyly in turnera ulmifolia l. (turneraceae)

Abstract

Turnera ulmifolia L. Is a polymorphic complex of diploid, tetrapioid and hexapioid varieties. Diploids and tetrapioids are distyious and hexapioids homostyious. A controlled crossing programme demonstrated that in diploids distyly is controlled by a single locus with two alleles. Long-styled plants are ss and short-styled plants can be either Ss or SS. In tetrapioids a similar pattern occurs with short-styled plants usually SSss and long-styled plants ssss. Tetrasomic inheritance was demonstrated by crosses with a SSss genotype synthesised by colchicine doubling. Double reduction could not be detected at the distyly locus. No significant deviation from a 1:1 morph ratio was observed in surveys of nine natural populations and progeny tests of 21 open-pollinated famiies from Brazil. Crosses between distyious and homostyious populations were undertaken to determine the inheritance of homostyly. The results were consistent with a model of supergene control. Clear segregation of phenotypes was observed in the F., and the dominance relationships S> h> s, where h is an allele that determines homostyly, were obtained. © 1985 The Genetical Society of Great Britain.