Evolution in an autopolyploid group displaying predominantly bivalent pairing at meiosis: genomic similarity of diploid Vaccinium darrowi and Autotetraploid V. corymbosum (Ericaceae)

Abstract

The genomic relationship between V. darrowi Camp (2n = 2x = 24) and V. corymbosum L. (2n = 4x = 48) was examined using an interspecific tetraploid hybrid, US 75, and representatives of the parental species. Two features in the background of US 75 led to the prediction that it was an allopolyploid: (1) the parental species are quite distinct morphologically and geographically, and (2) the diploid genome was incorporated into US 75 via an unreduced gamete. However, US 75 recently was shown to display tetrasomic inheritance using molecular markers. In the present cytological study, US 75 was found to have a lower than expected number of multivalents for an autopolyploid, although it had a significantly higher number of quadrivalents than its autotetraploid parent, V. corymbosum. Normal chromosome distributions were observed at anaphase I and II, and pollen viability was high. Our findings suggest that little genomic divergence has developed between the Vaccinium species and that the polyploids may freely exchange genes with sympatric diploid species via unreduced gametes. This pattern of hybridization could be an important component of evolution in all autopolyploid groups, making them much more dynamic than traditionally assumed.

Segregation Models for Disomic, Tetrasomic and Intermediate Inheritance in Tetraploids: A General Procedure Applied to Rorippa (Yellow Cress) Microsatellite Data

“…Tetrasomic inheritance was associated with exclusively bivalent pairing in Lotus corniculatus (Fjellstrom et al 2001), Vaccinium darrowi, and V. corymbosum (Qu et al 1998) and in colchicine-induced autotetraploid Brassica oleracea ( Jenczewski et al 2002).…”

Meiotic analysis of two putative polyploid species of Verben-aceae from Brazil

“…Such information can be used to construct cytogenetic maps and determine the evolutionary relationships among related species (De Wet 1979;Stevens and Bougourd 1991;Fukui and Nakayama 1996;Seijo and Fernandez 2001). Qu et al (1998) used meiotic analysis to study Vaccinium species and observed tetrasomic inheritance, as well as the formation of bivalents and multivalents by random pairing among four homologues and a high fertility, all in the same newly formed hybrid. Studies with Lantana camara populations from South Africa, the Caribbean and India have shown that this species is tetraploid (x = 11) and always has uni-, bi-, triand multivalents, (Tjio 1948;Sen and Sahni 1955;Raghavan and Arora 1960;Arora 1961;Sinha and Sharma 1984;Spies 1984;Sanders 1987;Ojha and Dayal 1992;Sinha et al 1995).…”

RFLP Markers for the Selection of Pollination-constant and Non-astringent (PCNA)-Type Persimmon and Examination of the Inheritance Mode of the Markers

“…Persimmon is known to be a hexaploid (2n = 6x = 90) (Namikawa and Higashi, 1928;Tamura et al, 1998;Zhuang et al, 1990b), but its genome composition remains to be clarified. Previously, Zhuang et al (1990a) suggested that persimmon might be an allohexaploid based on the observation of the formation of few multivalents during the meiosis of pollen mother cells; however, a lack of multivalents does not necessarily indicate disomic polyploidy in species with short chromosomes (Krebs and Hancock, 1989;Qu et al, 1998;Wolf et al, 1989). In fact, our previous report suggested the possible polysomic inheritance of RFLP markers (Kanzaki et al, 2001).…”