Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

POLYPLOIDIZATION EVENTS INDUCED BY INTERSPECIFIC HYBRIDIZATION IN ASTER SPP.

CAMMARERI M.*, FUSCO M.**, ERRICO A.*, CONICELLA C.**

* Department of Agronomy and Plant Genetics, University of Naples, Via Università 100, 80055 Portici , Italy

** CNR-IMOF, Research Institute for Vegetable and Ornamental Plant Breeding, Via Università 133, 80055 Portici, Italy

conicell@unina.it

sexual polyploidization, 2n gametes, AFLP

The genus Aster includes about 600 species characterized by different morphology (plant architecture, leaf shape and size, capitulum size and colour), photoperiod and environmental responses. The germplasm diversity represents a useful gene source for the breeding since a number of species and interspecific hybrids are grown as ornamentals.

Wide interspecific hybridization was performed among twelve wild species of Aster characterized by different chromosome number and ploidy. Although, the barriers to interspecific hybridization in Aster seem to be poorly developed, the capitulum morphology hampers strictly controlled crosses. Out of 182 putative hybrids, a sample coming from A. lateriflorus (2n=16) used as female parent was analysed by AFLP markers. The interspecific hybrids were selected on the basis of the presence of male parent-specific bands from the following species: A. caucasicus (2n=18), A. cordifolius (2n=16), A. foliaceus (2n=46), A. novae-angliae (2n=10), A. tongolensis (2n=52) and A. tripolium (2n=18). The hybrids were also analysed for chromosome number, pollen stainability, capitulum morphology and seed production. In four cross combinations, the hybrids exhibited a doubling of chromosome number probably due to unilateral and bilateral sexual polyploidization based on 2n gametes. Presence of 2n pollen was evidenced in both the parental species and hybrids; moreover, tetraploid forms of A. lateriflorus occur spontaneously deriving from 2n eggs and 2n pollen formation. As concerning capitulum morphology, the hybrids showed generally a reduction of ligulate florets and an increase in capitulum diameter as compared to the female parent.

In conclusion, sexual polyploidization seems to be an important mechanism of adaptation and speciation in Aster spp.