A green fluorescent protein-based screening method for identification of resistance in anthurium to systemic infection by Xanthomonas axonopodis pv. dieffenbachiae

Resistance of cultivars of Anthurium andraeanum to systemic infection by Xanthomonas axonopodis pv. dieffenbachiae , the causal organism of bacterial blight disease of anthurium, was investigated using a bioengineered bacterial strain containing p519ngfp plasmid. Successful infection establishment in anthurium was found to be cultivar and inoculum density dependent, but independent of plant age. Injection of cut petioles (stage-2 leaf) with 100  µ L inoculum (10⁹ CFU mL⁻¹) resulted in 100% infection establishment in susceptible cultivars on a repeatable basis, and differentiated between various levels of observed field resistance. Time to death (weeks) and proportion of dead plants best differentiated between levels of resistance and cultivars were placed in four groups based on these criteria. The susceptible group (32 cultivars) rapidly declined within 6–12 weeks of inoculation (WAI) and resulted in 100% plant death; the moderately resistant group (10 cultivars) declined within 12 WAI, but resulted in less than 100% plant death; the resistant category had less than 100% plant death with a slow decline taking over 20 weeks; and the highly resistant category (15 cultivars) showed 0% infection. The correlation coefficient between green fluorescent protein (GFP)-fluorescence and eventual death of plants was 0·90, indicating that the final death of individual plants can be reasonably well predicted based on GFP-fluorescence data at 5 WAI. Hence GFP data at 5 WAI can be used for early detection of latently infected plants and may assist screening for resistance in segregating populations of anthurium.