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 - 1.04

Characterization of microspore embryogenesis in anther culture of Citrus

Ramírez C.*, Chiancone B.**, Testillano P.*, Germanà M.A.***, Risueño M.C.*

*)Plant Development and Nuclear Organization Unit. Centro de Investigaciones Biologicas, C.S.I.C. Madrid (Spain)

ramirez@cib.csic.es ; mailto:risueno@cib.csic.es

**) Dipartimento di Colture Arboree. Facoltà di Agraria, Università di Palermo (Italy)

***) Istituto di Ricerca per la Genetica degli Agrumi, C.N.R. c/o Facoltà di Agraria. Viale delle Scienze 11, Palermo (Italy)

agermana@unipa.it

haploid, androgenesis, Citrus, gametic embryogenesis

Haploid plants have important interest for breeders and geneticists for their potential in mutation research, selection, genetic analysis and production of inbred lines, particularly in fruit trees characterized by a long reproductive cycle, a high degree of heterozygosity, large size and, often self-incompatibility.

To improve the induction rate (the frequency of microspores which form embryos) and to enlarge the number of respondent genotypes, are fundamental goals in order to make androgenesis a reliable tool in Citrus breeding. To understand the mechanisms of microspore embryogenesis in cultured anthers and the subsequent haploid plants formation could be fundamental in recalcitrant species like Citrus to increase the number of genotypes respondent to the phenomenon and to increase the induction rate. Androgenesis by anther or isolated microspore culture is the most widely used method to obtain haploid and double-haploid plants. By anther culture technique, haploid and doubled-haploid embryogenic calli, plantlets and in vivo grafted plants have been obtained in C. clementina Hort. ex Tan.

However there are not extensive studies in this system to characterize the process at cellular level.

This research has been carried out to characterize, at cellular and subcellular level from the morphological and ultrastructural point of view, the early stages of microspore embryogenesis in several cultivars of Citrus clementina (Nules, SRA 63 and Monreal) respondent to the androgenetic process. Microscopical analysis revealed very important aspects of this embryogenic process. Particularly it showed several differences between Citrus microspore derived embryoids and those derived from other gametic embryogenic species, like starch accumulation during the first embryonic stages. Moreover different cellular types have been detected in these embryoids after the exine rupture. Cytochemical assays for polysaccharides revealed the process of cell wall formation inside the small pro-embryos during the first embryonic stages. Immunogold labelling assays with antibodies recognising cell walls components, revealed a differential composition of young embryoid cell walls, probably in relation to differentiation processes.