Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2014
Publication Date: 6/15/2014
Citation: Clark, N., Frigulti, T., Zheng, Z., Wallis, C.M., Bushoven, J., Chen, J. 2014. Increase of “Candidatus Liberibacter solanacearum” titer in aging tomato leaves and pyrosequencing analyses of endophyte populations. Meeting Proceedings. p. 171-175. Interpretive Summary: “Candidatus Liberibacter solanacearum” (Lso) is thought to be the pathogen causing potato zebra chip disease, which causes significant losses for the US potato industry. Lso is a bacterium that cannot be cultured in artificial media, which makes it difficult to study. This project developed a procedure to maintain and increase Lso concentrations in tomato leaves. The method allowed Lso titers to increase up to 42-fold over a 28-day period. A next generation sequencing procedure, called pyrosequencing, was applied to the leaf DNA extract enriched with Lso. Analyses of the sequences determined that, in addition to Lso, another bacterium called pseudomonas also was likely present. The developed Lso enrichment procedure and discovery of a new bacterium associated with Lso will facilitate research aimed at reducing losses due to zebra chip disease.
Technical Abstract: This project studied changes in titer of “Candidatus Liberibacter solanacearum” (Lso) in tomato leaves of different cultivars with the goal of searching for factors associated with Lso enrichment. Lso titers, as monitored by qPCR, were observed to increase in tomato leaf cultures, which involved maintaining excised Lso-infected leaves in soil under greenhouse conditions. Lso titers on average increased 4.84 to 41.86 fold in leaves cultured for 28 days. Among the three cultivars tested for tomato leaf cultures, “Big Boy” consistently had higher Lso titer than the other cultivars. It was concluded that aging of tomato leaves provided a better environment for Lso growth. A pyrosequencing experiment using DNA extracted from Lso-enriched tomato leaves yielded 696,329 reads averaging 419 bp each. BLAST analyses with selected bacterial genomes showed that Lso ranked first among top-hit scores, as well as the mean of the top ten scores. Interestingly, a pseudomonas-like bacterium also was observed to be in abundance at levels similar to Lso.