| Pierce's disease (PD) of grapevine is caused by the bacterium Xylella fastidiosa (Xf) and is a limiting factor in grapevine production in California and the southeastern United States. Minimum Inhibitory Concentrations (MICs) were determined for inhibiting Xf growth on PD3 medium supplemented with plant micronutrients and antibiotics. Tetracycline at 1 ppm and streptomycin at 4 ppm exhibited the lowest MICs. Zinc sulfate had the lowest MIC value (16 ppm) of the micronutrients evaluated. Concentrations of micronutrients were determined following application on grapevines. One treatment, Zinc Metalosate(TM), was significant in reaching the MIC, in vitro, concentration. Several treatments caused significant increases in micronutrient concentration, but they did not achieve concentration to prevent Xf growth in vitro.; Plant micronutrients and antibiotics were evaluated for their ability to reduce PD symptoms in systemically infected field-grown grapevines. A single fall and spring application of a zinc-containing bactericide followed by severe pruning showed promise in treating PD-affected vines.; Culturable bacterial endophytes in healthy, PD-affected and PD-escape grapevines in Napa and Davis, California were studied. Numbers of endophytes obtained from all vine types ranged from 1.44 log cfu/ml to 1.76 log cfu/ml of xylem fluid. Bacteria were identified by sequence analysis of the 16S rDNA. Several Bacillus spp, Pseudomonas gramminis, Carnobacterium spp and Sphingomonas spp were among the dominant bacterial taxa isolated from grapevines. The most frequently isolated genus was Bacillus, representing a total of 23.4% of all bacteria isolated.; Endophytic bacteria were assessed for their ability to systemically colonize grapevine and their potential to act as biological control agents against Xf. Of the 24 endophytes exhibiting in vitro growth inhibition activity against Xf on PD3 medium, 13 also systemically colonized greenhouse grapevines. The majority of these bacteria were Bacillus spp. The others were members of the order Actinomycetales and a Rahnella spp.; A Pil E fusion protein from Xf was generated using the PurePro Caulobacter Expression Kit(TM) and synthetic peptides that bind to the recombinant Pil E protein were identified using the Ph.D.(TM) Phage Display Peptide Library Kit. Peptide binding was confirmed by ELISA. |
