Chromosome number and size variations in the Australian Salicornioideae (Chenopodiaceae)—evidence of polyploidisation

Abstract

New somatic chromosome counts were recorded from 27 accessions representing 21 Australian species across six genera, Halosarcia Wils., Pachycornia Hook.f., Sarcocornia Scott, Sclerostegia Wils., Tecticornia Hook.f. and Tegicornia Wils., in the subfamily Salicornioideae Ulbr. (Chenopodiaceae Venten.). The results indicated that the Australian Salicornioideae have a basic chromosome number of x = 9, congruent with other members of the Chenopodiaceae. Polyploidy is evident, particularly in the largest genus Halosarcia, ranging from diploid to hexaploid (2x = 18, 27, 36 and 54). With the exception of Pachycornia triandra (F.Muell.) Black, the chromosomes observed were 1.11–3.85 μm in length, with a total genome length of the haploid set of 13.82–23.16 μm. P. triandra had considerably larger chromosomes (3.09–5.57 μm) with a total genome length of the haploid set of 36.93 μm.

Intraspecific ploidy variation occurs in the mostly endemic genus Halosarcia, which is the largest genus in the subfamily. Diploid, triploid and tetraploid ploidy levels were detected in H. indica (Willd.) subsp. bidens (Nees) Wils. sampled from separate populations and two ploidy levels were recorded in seedlings germinated from individual H. leptoclada Wils. and H. pterygosperma (Black) Wils. adults. The presence of polyploidy in Halosarcia may provide a mechanism that fosters diversity and phenotypic variation.