Karyotype analysis in Stylidium crossocephalum (Angiospermae:Stylidiaceae)

Abstract

Qualitative studies of karyotypes were carried out on 79 plants of Stylidium crossocephalum from 28 collection sites. The sample included 7 distinct karyotypic classes which could be resolved into 5 clearly distinguishable haploid karyotypes or genomes. Three genomes, J, K and L, were localised in an area covering a southern portion of the species range while the other two genomes, A and B, were found in a region 90km to the north. Two different genome heterozygotes were found, one characterised by a J/K karyotype, the other by an A/B karyotype. —Karyotypic studies of a synthetic hybrid and its two parents showed that the chromosomes of the constituent genomes of the hybrid could be readily and confidently discerned in the karyotypes of the parents. These studies demonstrated that the identification of genomes by the qualitative attributes of their constituent chromosomes constitutes a reliable analytical technique. — Statistical analyses using arm ratio and percentage length measurements of chromosomes from plants allocated to the two groups of genomes confirmed the differences between marker chromosomes and demonstrated additional statistically significant differences among the non marker chromosomes. Some of these statistical differences may be attributable to technical problems inherent in the karyotyping procedures. In two instances, however, they could be convincingly argued as real, demonstrating a further component of chromosome variation in S. crossocephalum.