Xanthomonas arboricola pv. corylina - identification of the pathogen and population biodiversity

Abstract

Bacterial blight of hazelnut, caused by Xanthomonas arboricola pv. corylina (Xac), is the most important bacterial disease of this nut crop worldwide. In our country, after the disease was initially described in the 1950s, there were no further data about the research of this pathogen. During the growing season of 2008-2011, symptoms of leaf spots, bud and twig necrosis and dieback, suggesting bacterial infection, were observed on hazelnut plants in several localities in Serbia. In order to study etiology of disease, symptomatic samples of diseased hazelnut plants were collected from different hazelnut-growing regions in the country. Isolations from the diseased tissue resulted in Gram and oxidase negative, catalase-positive, aerobic yellow bacterial colonies. Total of 47 representative strains were selected for further study. Strains isolated from hazelnut in Poland and various reference strains of Xac originating from international collections were also included in research. Based on their morphological, pathogenic, biochemical, physiological, serological and genetic characteristics tested strains were identified as Xanthomonas arboricola pv. corylina. Bacterial colonies formed on NA medium were small and glistening and on glucose amended GYCA medium large, mucous and domed. All strains hydrolyzed starch, gelatin and esculin, used glucose, maltose, sucrose as a carbon source, but not sorbitol, metabolized quinates, developed at 35 °C in the presence of 2% NaCl. The strains induced hypersensitive reaction of tobacco, tomato leaves and bean pods. Pathogenic nature of the strains was confirmed in pathogenicity test on host plants by reproduction of symptoms similar to natural infection. Based on carbon source utilization, metabolic diversity of investigated strains was confirmed. Strain's metabolic profiles were specific for Xanthomonas genus. Serological methods (ELISA i IF test) indicated similarity in serological characteristics among the studied strains, as well as the control Xac strain...

Bakteriozna plamenjača leske, čiji je prouzrokovač fitopatogena bakterija Xanthomonas arboricola pv. corylina (Xac), najznačajnije je bakteriozno oboljenje ove jezgraste voćke u svetu. U našoj zemlji bolest je prvi put uočena 50-ih godina prošlog veka, nakon čega nije bilo daljih proučavanja ovog patogena. U periodu 2008 - 2011. godine, u nekoliko rejona gajenja leske u Srbiji uočena je pojava simptoma pegavosti lišća, nekroze i uvelosti pupoljaka i letorasta, koji su ukazivali na moguću bakterioznu prirodu oboljenja. Simptomatični uzorci obolelih biljaka prikupljeni su sa različitih lokaliteta u našoj zemlji sa ciljem utvrđivanja etiologije oboljenja. Iz zaraženog biljnog tkiva izolovani su Gram i oksidaza negativni, katalazapozitivni aerobni sojevi bakterija žute boje kolnija na HA podlozi. Za dalji rad odabrano je ukupno 47 reprezentativnih sojeva, koji su proučeni primenom standardnih i savremenih metoda. U istraživanja su uključeni i sojevi poreklom iz Poljske, kao i referentni sojevi Xac poreklom iz međunarodnih kolekcija. Detaljno su proučene morfološke, patogene, biohemijsko-fiziološke, serološke i genetičke odlike sojeva, na osnovu kojih su svi proučavani sojevi identifikovani kao Xanthomonas arboricola pv. corylina. Na podlozi od hranljivog agara (HA) formirane su sitne i sjajne kolonije, dok su one na podlozi obogaćenoj glukozom (GYCA) bile krupne, sluzaste i ispupčene. Svi proučavani sojevi hidrolizuju skrob, želatin i eskulin, koriste glukozu, maltozu, saharozu kao izvor ugljenika, ali ne i sorbitol, metabolišu kvinate, razvijaju se pri 35°C i u prisustvu 2% NaCl. Sojevi su prouzrokovali hipersenzitivnu reakciju na listovima duvana i paradajza i mahunama boranije. Patogenost sojeva potvrđena je testom patogenosti na domaćinu i reprodukcijom simptoma prirodne infekcije. Na osnovu Biolog testa utvrđena je raznovrsnost proučavanih sojeva čiji su metabolički profili bili specifični za rod Xanthomonas...