Identification of Pectobacterium carotovorum as the causal agent of bacterial canker on Pyrus communis L in Brazil
Yuliet Franco Cardoza: Agronômica - Laboratório de Diagnóstico Fitossanitário e Consultoria
<div>In June 2016, bacterial canker-like symptoms were observed on <em>Pyrus</em> <em>communis</em> L cv. Yali in one commercial orchard in Monte Castelo, SC. Eight-hundred of 1.200 plants were lost by death and, finally, tree eradication. In affected trees, the disease manifested as cankers with exudates on trunks and twigs, and the stems turned brown and slowly died. Bacteria were isolated on King B medium from infected tissues. Biochemical tests including Biolog® GEN III were conducted and some isolates were selected for whole genome sequencing throught Ion Torrent™ platform. PCR with Y1/Y2 and PcaF/PcaR primers, specific for <em>P. carotovorum</em> and <em>P. carotovorum </em>subsp. <em>actinidiae</em> respectively were also carried out. A total of 15 bacterial colonies were isolated from infected tissues. All were gram-negative, facultatively anaerobic, rod-shaped and exhibited a strong pectolitic activity in potato and carrot disks. Biolog assay showed that the isolates were homogeneus, and three of them were selected for further tests. The organism with the highest genome and proteome identity (99.8%) with the isolates was <em>Pectobacterium carotovorum</em> subsp. <em>actinidiae</em>. A product of the expected size was obtained in both especific PCR. Inoculation of pear tree branches with 24h old colonies showed that the bacterium was able to colonize the plant tissues. More tests, including kiwifruit inoculation, are in progress to fulfill Koch’s postulates. To our knowledge, this is the first report of <em>P. carotovorum</em> causing pear bacterial canker-like symptoms in Brazil. Identification and monitoring of this pathogen is very important due to large economic losses that can cause.</div>
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