Relationship between Symptom Development and Actual Sites of Infection in Leaves of Anthurium Inoculated with a Bioluminescent Strain of Xanthomonas campestris pv. dieffenbachiae

Abstract

The infection process of bacterial blight of anthurium was monitored with a bioluminescent strain of Xanthomonas campestris pv. dieffenbachiae. The relationship between symptom expression on infected leaves (assessed visually) and the extent of bacterial movement within tissues (evaluated by bioluminescence emission) varied among anthurium cultivars. In several cultivars previously considered susceptible on the basis of symptom development alone, bacterial invasion of leaves extended far beyond the visually affected areas. In other cultivars previously considered resistant, bacterial invasion was restricted to areas with visible symptoms. In three cultivars previously considered resistant, leaves were extensively invaded by the bacterium, and yet few or no symptoms were seen on infected leaves. The pathogen was consistently recovered from leaf sections emitting bioluminescence but not from sections emitting no light. At an early stage of infection, no significant differences in the percentages of infected areas as determined by visual assessment were observed in any of the cultivars. However, differences among cultivars were detected by bioluminescence as the disease progressed, because bacterial invasion was not always accompanied by symptom expression. In susceptible cultivars, the advancing border of infection was 5 to 10 cm inward from the margins of the visible symptoms and often reached to the leaf petiole even when symptoms were visible in <10% of the total leaf area. Comparisons of anthurium cultivars in which a nondestructive method was used to quantify the severity of leaf infection by a bioluminescent pathogen have enabled us to evaluate susceptibility and resistance to bacterial blight accurately. Such evaluations will be of importance in breeding resistant cultivars for disease control.

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

“…Both spray inoculation of leaves and root inoculation were used successfully to infect anthurium in Hawaii (Fukui et al ., 1996) and in the Caribbean (Prior et al ., 1985), but spray and root inoculation was reported to be ineffective in reliably establishing systemic infection in a later study (Anaïs et al ., 2000). Fukui et al (1998) described an effective method of infection establishment through cut-petiole ends, which could also be used to detect latent systemic infection using a bioluminescent strain of X .…”

Suppression of Bacterial Blight by a Bacterial Community Isolated from the Guttation Fluids of Anthuriums

“…Cultivar Marian Seefurth plants were used in the experiment performed to determine the effects of guttation bacteria on the ability of Xcd-lux to infect anthurium leaves. This cultivar is known to be highly susceptible to bacterial blight (5). The experiment consisted of the following four treatments (10 plants per treatment, one leaf per plant): leaves that were treated with bacteria and wounded (by notching at four sites around the leaf margin); leaves that were not treated but were wounded; leaves that were treated with bacteria and not wounded; and leaves that were not treated and not wounded.…”

“…The remaining plants in each treatment group were neither wounded by notching nor inoculated with the bacterial mixture. After the treated leaves were dried at room temperature, all of the plants were spray inoculated with a suspension of Xcd-lux cells (concentration, ϳ10 6 CFU/ml) as described previously (5). The next day, the plants were arranged in a complete randomized design in the glasshouse.…”

“…dieffenbachiae has provided valuable information on the infection process in bacterial blight, especially during the latent systemic phase of infection (4). Use of the bioluminescent strain has also allowed accurate evaluation of cultivar susceptibility in the foliar infection phase without dependence on symptom expression (5). While conducting susceptibility evaluation tests in the greenhouse, we observed that the severity of leaf infection in a certain cultivar occasionally was unusually variable in replicates.…”

“…Changes in cultural practices, as well as strict sanitation (15), have reduced the disease problem to manageable levels. Yet, bacterial blight has not been eradicated from production fields, since the mild climate and persistent latent infections perpetuate the disease in symptomless plants (5,17). Also, the pathogen can be introduced into clean fields by aerosols (2).…”