Author : Zarate, Jocelyn T.

Summary : The tomato R. solanacearum substrain T731 of strain T523, wilted resistant variety HAwaii 7996 confirmed its hypervirulence. both were virulent on susceptible tomato varieties L390 and Bonny best and similar in their ability to cause hypersensitive response, motility, cellulase, pectinase and phospholipase enzyme activities, growth in culture and in planta. both belong to Phylotype I and to the same sequevar group based on endoglucanase gene sequences. PFGE showed three differential bands between the two strains. Cloned and sequenced unique 418 bp REP PCR band from strain T731 is present in two positions in strain GM11000 megaplasmid (1) downstream of ISRso13 and a peripheral hypothetical protein and (2) overlapping a probable transmembrane protein. In silico analysis of REP-PCR product showed bacterial promoter and motifs similar to GATA binding factors. BIOLOG phenotype microarray showed higher level of quinic acid degradation by strain T731. Quinic acid is a key intermediate in the biosynthesis of aromatic compounds that are plant defense signals. Degradation may lead to lower resistance of plants. Higher level of degradation of homoserine lactone by strain T731 suggests possible mutation in the SolR component of the Soll/SolR signal transduction mechanism, a transcriptional regulator that respond to sufficient quantities of homoserine lactones by increasing transcriptional activity of target promoters including induction of virulence cascade.