6533b7d1fe1ef96bd125c77d

RESEARCH PRODUCT

STUDY ON ISOLATED MICROSPORE CULTURE IN CITRUS SINENSIS L. OSBECK CV. MORO, A BLOOD ORANGE CULTIVAR

subject

description

In vitro tissue culture represents a useful support for the advancement of Citrus breeding and propagation. Haploidy technology, that is the single-step development of complete homozygous genotypes from heterozygous parents through gametic embryogenesis, has already a huge impact on many relevant crops, representing an integral part in their breeding programmes (Germanà 2011a; 2011b). In order to increase the number of genotypes responding to gametic embryogenesis, in vitro isolated microspore culture of Citrus sinensis L. Osbeck cv. Moro, has been carried out, investigating the influence of the culture medium composition, and, particularly, of the plant growth regulator types and concentrations. Meta-topolin, a naturally occurring aromatic cytokinin, is considered an alternative to benzyladenine (BA), zeatin (ZEA) and kinetin (KIN) in plant tissue culture (Aremu et al., 2012), and it is used, mainly, to increase the efficiency of in vitro plant propagation of several species, among them also Citrus (Niedz and Evens, 2011). In this study, metatopolin has been added to the culture medium in substitution of BA and ZEA. After seven months of culture, for all the media tested, different structural features have been observed and registered: microspores uninucleated with no development, binucleated with two asymmetrical nuclei (normal gametophytic pathway: one vegetative and one generative nucleus), binucleated with two equal-size vegetativetype nuclei that had just started their sporophytic pathway, trinucleated, tetranucleated, multinucleated, and, for the first time, calli and embryos at different stages have been obtained. These results indicate an advancement in the knowledge of pollen embryogenesis in Citrus sinensis L. Osbeck cv. Moro. Actually, this is the first time that embryo regeneration from isolated microspore cultures has been reported in sweet orange, a genotype markedly recalcitrant to pollen embryogenesis.