Evaluation of citrus rootstock transgenic for rolABC genes

Modification of tree architecture and reduction of tree size are aims of great value in citrus genetic improvement. For citrus, in fact, few dwarfing rootstocks are available, though a reduction of canopy size can be nowadays achieved with viroids inoculation. Recently with the aim of modifying growth habit of an important rootstock, rolABC genes isolated from Agrobacterium rhizogenes were introduced into 'Troyer' citrange determining plants with a reduced development. In this work we evaluated molecular, morphological and physiological aspects of the transgenic rootstock. To further confirm the increased rooting ability of this transgenic clone, cutting experiments were carried out. In order to evaluate the dwarfing effect of transgenic rootstock on the scion, ten transgenic plants were grafted with a vigorous nucellar line of 'Tarocco' orange; growth habit and development of the scion were monitored. To better understand the metabolic alterations caused in transgenic citrange by rol genes, relative transcript levels of genes involved in hormonal biosynthetic pathway were quantified by Real-Time PCR. The results obtained showed that rolABC genes influenced plant development modifying the phenotype of citrange, establishing an appreciable reduction of the size and influencing the growth habit of the 'Tarocco' scion.