Poster: Plant-pathogen interactions
Abs #
573: Genetic transformation of Citrus paradisi (cvs. Duncan, Flame, Marsh, and Ruby Red) with p23 sequence from the genome of Citrus Tristeza Closterovirus
Citrus Tristeza Virus (CTV) is the most important virus disease of citrus worldwide. Grapefruit (Citrus paradisi Macf.) cultivars with improved CTV tolerance or resistance are needed to manage CTV-induced diseases. We have employed Agrobacterium tumefaciens-mediated genetic transformation to introduce p23 sequence from the genome of CTV into grapefruit in an effort to produce plants with altered resistance to CTV. Agrobacteria that were used in these experiments carried binary vectors harboring the hairpin structure consisting of two inversely repeated p23 sequences (pTLAB-10) and p23 with a part of 3’ untranslated region (pTLAB-14). Both binary vectors carried GUS as a reporter gene and nptII as a selection gene for prospective transgenic shoots. Epicotyl explants were incubated in suspensions of appropriate Agrobacteria and left on selective medium for 4 weeks. Overall shoot morphogenesis index (SMI) was 29.1 for pTLAB10, and 76.7 for pTLAB14 plasmids. Green shoots that were found on explants after 4-5 weeks following the incubation with bacteria were tested for the presence of GUS gene by histochemical analysis. The percentage of GUS-positive shoots and transformation efficiency was 13.1% and 1.0% for pTLAB10 and 28.3% and 1.2% for pTLAB14. GUS-positive shoots were micro-grafted on Carrizo rootstock. Subsequently, the presence of desired sequences in grafted GUS-positive plants was confirmed by PCR. Resistance of transgenic plants obtained until now is being evaluated by in vitro inoculation of CT-virus into protoplasts obtained from leaves.
