title: Genetics of self incompatibility in diploid Ageratum houstonianum mill.
abstract: Diallels and backcrosses among self-incompatible (SI) clones and progeny of Ageratum houstonianum Mill. could be organized into intra-incompatible classes. Four of 5 progenies segregated in expected ratios of S genotypes. Ageratum expressed a one-locus incompatibility system of the sporophytic type with a linear dominance series of multiple alleles and complete allelic dominance in both pollen and stigma. In the second part of the study, a high percentage of self-seed set was observed during the first flowering of a progeny from a pseudo-self compatible (PSC) seed source. Six progenies were derived from the PSC seed source. Five of the 6 segregated PSC ∶ SI plants, 4 of which fit a 3 ∶ 1 ratio of PSC ∶ SI plants. All plants of the sixth progeny were SI. Two F1 progenies with the same PSC pollen parent produced significantly different segregations of PSC ∶ SI plants. It appeared that PSC acted as a major gene when the most recessive S allele was also present, but PSC was not expressed when the most dominant S allele was present. Clones propagated from PSC plants were SI and cross incompatible with a related S-allele tester. Thus, PSC was transient in that it was apparent in seed-propagated plants but not in plants clonally propagated from the PSC individuals.
authors.affiliation: Department of Horticultural Science and Landscape Architecture, University of Minnesota, St. Paul, Minnesota, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Stephens
authors.forename: P D
authors.initials: PD
authors.lastname: Ascher
authors.forename: R E
authors.initials: RE
authors.lastname: Widmer