Xylella fastidiosa in Rabbiteye Blueberry: Detection of the Bacterium and Association with Yield Loss

Previous greenhouse work at the University of Georgia suggested that Xylella fastidiosa was not a major concern in rabbiteye (Vaccinium ashei Reade) blueberry. Sampling of twenty orchards in Louisiana and Mississippi, however, has revealed infection in a limited number of orchards, in rabbiteye bushes in various states of vigor. Analysis of data collected on forty naturally infected or non-infected plants (V. ashei ‘Tifblue’) in Louisiana during the 2013 and 2014 seasons revealed a significant difference in total yield per plant between those in which X. fastidiosa was (5.2 kg, n = 9) and was not (12.8 kg, n=31) detected. The difference in average berry weights, based on 25 berry samples at each harvest date, was marginally significant, with berries from X. fastidiosa-positive plants averaging 1.3 g and those from X. fastidiosa-negative plants averaging 1.4 g. Soluble solids concentrations were higher, on average, in X. fastidiosa-positive (11.5%) than X. fastidiosa-negative (10.1%) plants, based on a non-parametric analysis of samples from one harvest date in 2014. Plant samples taken bimonthly have revealed variation in the detectability of the pathogen in different plant parts. Repeated sampling of two plants from February through June suggested that detection of X. fastidiosa by real-time polymerase chain reaction (qPCR) on DNA from root sap was more reliable than detection by qPCR on DNA from stem sap or by enzyme-linked immunosorbent assay (ELISA) on petiole/midrib tissues or most recent shoot growth (sampled when leaves were absent). Tracking of detectability of the pathogen continues, with an increased sample size. Additional work is being done to determine the genotype(s) of X. fastidiosa isolates from rabbiteye blueberry and to identify rabbiteye cultivars that are resistant or tolerant to X. fastidiosa.