Erwinia amylovora – the Causal Agent of Root Collar Necrosis of Apple Trees
Erwinia amylovora – prouzrokovač nekroze korenovog vrata stabla jabuke
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Author
Gavrilovic, Veljko
Milijasevic, Svetlana
Todorovic, Biljana
Zivkovic, Svetlana
Trkulja, Nenad
Keywords
Erwinia amylovoraApple
Necrosis
Root collar
jabuka
nekroza
korenov vrat
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Show full item recordAbstract
A large-scale outbreak of fire blight symptoms caused by Erwinia amylovora was recorded
in pome fruit trees during 2007. In addition to fruit necrosis and shoot blight as the typical
disease symptoms, dark purple necrosis was observed in the root collar area girdling the
trunk just above the ground and thus withering the whole apple tree. Since similar symptoms
on apple trees could be caused by E. amylovora or one of several phytopathogenic
fungi of the genera Phomopsis and Phytophthora, an investigation was conducted to identify
the causal agent of this disease. Levan-producing, nonfluorescent bacteria were isolated
from diseased samples. The isolated strains produced HR in tobacco leaves and necrosis
of artificially inoculated, immature pear fruits, followed by oozing of bacterial exudate,
a characterisitic of E. amylovora. Based on the results of pathogenicity tests, biochemical
characteristics, ELISA test and PCR analysis, it was confirmed that the investigated strains
belonged to E. amylovora, causing the root collar necrosis of apple trees as an atypical
symptom of this bacterium in Serbia.
The explanation of this symptom may be that the vegetative rootstocks were infected
with E. amylovora. Therefore, the development of diagnostic protocols for detection of E.
amylovora in apple rootstock is very important for health inspections of planting materials. Tokom 2007. godine zabeležena je masovna pojava bakteriozne plamenjače jabučastih
voćaka prouzrokovana bakterijom Erwinia amylovora. Pored nekroze plodova i plamenjače
mladara, tipičnih simptoma bolesti, našu pažnju je privukla pojava nekroze mrkoljubičaste
boje u zoni korenovog vrata, koja prstenasto zahvata prizemni deo i prouzrokuje izumiranje
stabala jabuke. S obzirom na to da uzrok ovakvih patoloških promena može da bude E.
amylovora, ali i fitopatogene gljive iz rodova Phomopsis i Phytophthora, preduzeta su istraživanja
sa ciljem da se utvrdi etiologija ovog oboljenja jabuke. Iz obolelih uzoraka izolovane
su bakterije koje stvaraju levan, ali ne i fluorescentni pigment. Proučavani sojevi prouzrokovali
su HR na listovima duvana i nekrozu inokulisanih, nesazrelih plodova kruške, uz obilno
stvaranje bakterijskog eksudata, što je karakterističan znak E. amylovora. Na osnovu rezultata
dobijenih pri testovima provere patogenosti, ali i rezultata biohemijskih odlika, ELISA
testa i molekularnih metoda (PCR), potvrđeno je da proučavani izolati pripadaju bakteriji
E. amylovora, koja je uzročnik simptoma nekroze korenovog vrata stabala jabuke, prvi put
zabeleženih u Srbiji. Moguće objašnjenje ove pojave je da su vegetativne podloge za kalemljenje
bile inficirane ovom bakterijom. Zbog toga je veoma bitno razvijati dijagnostičke
protokole za utvrđivanje prisustva E. amylovora u podlogama za kalemljenje jabuke, tokom
procesa kontrole zdravstvene ispravnosti sadnog materijala.