Morphological and physiological effects of rolABC genes into citrus genome

For citrus, unlike other fruit tree species, there are no useful dwarfing rootstocks available and the existing ones had serious limitations in their use because of their low adaptability to different environmental conditions or scions incompatibility. For this reason, obtaining dwarfing genotypes is one of the most important goals in citrus genetic improvement. With the aim of modifying the growth habit of an important rootstock, a research program was set up to introduce rolABC genes from Agrobacterium rhizogenes into the genome of Troyer citrange [C. sinensis (L.) Osb x Poncirus trifoliata (L.) Raf.]. Seedling stem segments were infected with Agrobacterium tumefaciens carrying pDN3514 plasmid with rolABC genes, GUS and nptII. Transgenic shoots were analyzed by PCR and RT-PCR. PCR positive shoots were micrografted or selfrooted and the transgenic plantlets were acclimatized in greenhouse. Five grafted and 25 selfrooted plants were obtained. Transgenic clones showed a dwarfing habit as the plant height was reduced to half of the control due to strong reduction of internodal stem length. Photosynthetic activity and other physiological parameters were also influenced.