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 - 1.03

THE USE OF TRIPLOIDY IN CITRUS BREEDING PROGRAM

RUSSO G., RECUPERO S., PUGLISI A., PIETRO PAOLO D., REFORGIATO RECUPERO G.

Istituto Sperimentale per l’Agrumicoltura, Corso Savoia, 190, 95024 Acireale, Italy

Citrus, breeding, triploid hybrids

The constitution of triploid hybrids started at ISA in Acireale in 1978. The strategy used has been to cross a monoembryonic 2x female parent with a 4x male parent. The unbalance between embryo and endosperm ploidy (3:4) makes these seeds from such crossings incapable to germinate in vivo. However the in vitro cultivation has been used for the rescue of the embryos.

Tetraploid parents are duplex because they originate from the doubling of the nucella or of other somatic tissues. Their genetic constitution in the segregation and recombination process that originates triploid hybrids determines characteristics nearer to the 4x parent than the 2x one. On the contrary the diploid progenies of citrus owing to the heterozygosis of the parents have very different characteristics from those of the parents, which often prevents their usage. In previous crosses of 2x X 2x with the aim to transfer the characteristic of resistance to mal secco in true lemons, the obtained hybrids, even if partly showing a good tolerance to disease, were practically unusable because their fruits were so dissimilar to a lemon. Using a tetraploid male parent (Doppio Lentini lemon) and a diploid female parent (C. limon X Pera del Commendatore) highly tolerant towards mal secco, a triploid hybrid (C3869) was obtained for the first time, with fruit characteristics very similar to a true lemon. In addition the fast growth of the fruit makes this hybrid very interesting for its early picking time in September. We emphasize the importance of this strategy to obtain seedless hybrids similar to a parent as in the backcross after some generations.

The main characteristics of some hybrids patented (Tacle, Clara, Reale) and others 32 promising ones under evaluation are reported.