In vitro tissue culture represents a useful support for the advancement of Citrusbreeding and propagation. Haploidy technology, that is the single-step developmentof complete homozygous genotypes from heterozygous parents through gameticembryogenesis, has already a huge impact on many relevant crops, representing anintegral part in their breeding programmes (Germanà 2011a; 2011b). In order toincrease the number of genotypes responding to gametic embryogenesis, in vitroisolated microspore culture of Citrus sinensis L. Osbeck cv. Moro, has been carriedout, investigating the influence of the culture medium composition, and, particularly,of the plant growth regulator types and concentrations. Meta-topolin, a naturallyoccurring aromatic cytokinin, is considered an alternative to benzyladenine (BA),zeatin (ZEA) and kinetin (KIN) in plant tissue culture (Aremu et al., 2012), and it isused, mainly, to increase the efficiency of in vitro plant propagation of severalspecies, among them also Citrus (Niedz and Evens, 2011). In this study, metatopolinhas been added to the culture medium in substitution of BA and ZEA. Afterseven months of culture, for all the media tested, different structural features havebeen observed and registered: microspores uninucleated with no development,binucleated with two asymmetrical nuclei (normal gametophytic pathway: onevegetative and one generative nucleus), binucleated with two equal-size vegetativetypenuclei that had just started their sporophytic pathway, trinucleated,tetranucleated, multinucleated, and, for the first time, calli and embryos at differentstages have been obtained. These results indicate an advancement in theknowledge of pollen embryogenesis in Citrus sinensis L. Osbeck cv. Moro. Actually,this is the first time that embryo regeneration from isolated microspore cultures hasbeen reported in sweet orange, a genotype markedly recalcitrant to pollenembryogenesis.
|Number of pages||1|
|Publication status||Published - 2014|