2019 ASHS Annual Conference

Ralstonia solanacearum is the causal agent of bacterial wilt, a disease with devastating effects on a wide host range of plants including members of the Ericaceae family. An aggressive population of R. solanacearum (currently renamed as Ralstonia pseudosolanacearum) has been shown to infect highbush, lowbush, rabbiteye and wild type blueberries with devastating effects. The objective of this project is to demonstrate that photosynthesis is reduced in blueberry highbush Arcadia™ ‘FL07-399 when R. pseudosolanacearum strain P824 (sequevar 13) infects the host, even in the absence of visible disease symptoms. Fluorometers have been developed which measure fluorescence yield under ambient light conditions and even under full sunlight. This allows for very sensitive fluorescence measurements in greenhouse and field and to evaluate reductions of photosystem II (PSII) activities caused by stress. These results will allow early detection of the disease in blueberry plants or hidden reservoirs in tolerant plants. Eight plants were inoculated with P824 bacterial suspensions by cutting the stem and applying 10^3 cells to the wound site. Plants were maintained in a greenhouse with controlled temperature and lighting for 45 days. At the end of the experiment a LI-COR6800 fluorometer was used to measure CO2 levels and fluorescence by measuring 3 apical leaves per plant with 5 readings per leaf. Bacterial populations are being isolated from stems of symptomatic and asymptomatic plants to confirm infection. Preliminary analysis shows differences in CO2 output between symptomatic and asymptomatic plants. We expect to confirm that photosynthetic activity is reduced in infected plants even in the absence of symptoms.