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

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 4.35

EXPLOITATION OF INCONGRUENT SOLANUM SPECIES FOR INTROGRESSION OF LATE BLIGHT RESISTANCE INTO THE CULTIVATED POTATO

IOVENE M., AVERSANO R., CARPUTO D., FRUSCIANTE L.

Department of Soil, Plant and Environmental Science, School of Biotechnology Sciences, Via Università 100, 80055 Portici, Italy

potato, wild species, resistance to biotic stresses, sexual hybridization, somatic hybridization

Wild Solanum species play a key role in potato breeding, having traits such as resistance to biotic and abiotic stresses and high dry matter content of tubers lacking in the standard varieties. In this study, sources of resistance to Phytophthora infestans have been investigated in the diploid (2n=2x=24) S. brachystotricum (bst), S. bulbocastanum (blb) and S. cardiophyllum (cph) wild species, and resistant clones within each of them have been selected. Unfortunately, post-zygotic barriers hamper the exploitation of these species, which cannot be directly crossed with S. tuberosum (tbr) haploids (2n=2x=24), unless their somatic chromosome complement is doubled or alternative breeding strategies are employed. Two different approaches have been carried out to overcome these incompatibility barriers: (1) sexual hybridization through in vitro manipulation of wild species ploidy level, and (2) somatic hybridization through protoplast electrofusion. Chromosome doubling of selected resistant blb and cph clones has been obtained through a cycle of in vitro explant regeneration, with doubling frequencies of 39% and 55%, respectively. Bst has not regenerated. The tetraploid regenerants are now being used in crosses with tar haploid to produce tripled “bridges”. As for somatic hybridisation, parental protoplasts have been electrofused in AC/DC. In electrofusion, an AC field is first applied to align protoplasts, then membrane fusion between contacting protoplasts is allowed by three consecutive DC pulses. Regenerants from fusion between the wild blb and cph and tbr haploids have been obtained with regeneration frequencies (referred to the number of calli transferred to regeneration media) of 0.7% and 4.5%, respectively. Among these regenerants, somatic interspecific hybrids are being identified through RAPD species-specific markers.