Pyrosequencing analyses of endophytic bacterial populations in tomato leaves infected by ‘Candidatus Liberibacter solanacearum’
N. CLARK (1), T. L. Frigulti (1), J. Bushoven (2), Z. Zheng (3), C. Wallis (4), J. Chen (5). (1) California State University, Fresno, CA, U.S.A.; (2) California State Univerisity, Fresno, CA, U.S.A.; (3) South China Agricultural University, Guangzhou, China; (4) USDA-ARS, Parlier, CA, U.S.A.; (5) USDA ARS PWA, Parlier, CA, U.S.A.
‘<i>Candidatus</i> Liberibacter solanacearum’ (CLso) is associated with zebra Chip (ZC) disease of potato. The bacterium is currently not culturable and commonly maintained in plant hosts for characterization. This also provides an opportunity to study interactions between CLso and other endophytic bacteria. In this study, CLso was graft-transmitted to tomato plants. A maximum of over 200-folds titer increase was obtained by maintaining excised tomato leaves in potting soil for 28 days under greenhouse conditions. Metabolism changes in tomato leaves were also monitored. Preliminary results revealed that sucrose levels were over 60% greater in leaves at date 28 than when initially moved into potting soil. DNA was extracted from CLso-enriched tomato leaves and subjected to pyrosequencing. A total of 100,867 reads averaging 419 bp each was generated. BLAST (Basic Local Alignment Search Tool) analyses, using 43 selected whole genome sequences covering all major categories of prokaryotes in GenBank database as queries, revealed that bacterial sequences similar to CLso, <i>Pseudomonas putida</i>, and <i>Streptomyces davawensis</i> were highly abundant. PCR experiments further confirmed simultaneous co-enrichment of these bacteria. This is the first observation on the association of Pseudomonas-like and Streptomyces-like bacteria with CLso titer increase in tomato plants.
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