Plasmopara obducens – a New Threat to the Production of Impatiens walleriana in Serbia
Plasmopara obducens – nova pretnja proizvodnji Impatiens walleriana u Srbiji
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Author
Ristic, Danijela
Vucurovic, Ana
Stankovic, Ivana
Jovic, Jelena
Milojevic, Katarina
Bulajic, Aleksandra
Krstic, Branka
Keywords
Impatiens wallerianaDowny mildew
Morphology
Molecular identification
Phylogenetic analysis
plamenjača
morfološke karakteristike
molekularna identifikacija
filogenetske analize
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During 2010, Impatiens walleriana plants with symptoms of downy mildew were collected
in a greenhouse in the vicinity of Mionica, Kolubara District. Disease incidence was
extremely high, approaching 100%, and wilting and collapse of affected plants was very
rapid, resulting in losses of more than 90%. White downy growth produced on the lower
leaf surface consisted of hyaline, thin–walled sporangiophores with monopodial branching
and numerous, ovoid and hyaline sporangia. Apical branchlets of sporangiophores
were at right angles to the main axis, with no apical thickening. Pathogenicity tests included
inoculation of young I. walleriana plants by spraying with a sporangial suspension, and
downy mildew symptoms were observed after 13 to 15 days. The absence of well–defined
spots on the infected impatiens leaves and straight sporangiophores indicated that the
pathogen was P. obducens, which was further supported by molecular identification, the
5’–end of the nuclear DNA coding for the large ribosomal subunit (LSU rDNA) was amplified
by PCR, using primers NL1 and NL4. A representative isolate, 28–10, was sequenced and
phylogenetic analysis showed its grouping with other P. obducens isolates of different origin.
Considering that impatiens downy mildew in Serbia is proved to be caused by P. obducens
it is necessary to employ adequate phytosanitary measures to prevent further spread
of the pathogen. Tokom 2010. godine biljke Impatiens walleriana sa simptomima plamenjače sakupljene
su u stakleniku u okolini Mionice, Kolubarski okrug. Učestalost oboljenja bila je izuzetno
visoka, blizu 100%, a sušenje i propadanje zaraženih biljaka veoma brzo, što je dovelo
do šteta većih od 90%. Bela prevlaka patogena koja se razvijala na naličju listova sastojala
se od hijalinskih monopodijalno razgranatih sporangiofora sa tankim zidovima i brojnih,
ovoidnih i hijalinskih sporangija. Vrhovi grana sporangiofora granali su se pod pravim
uglom u odnosu na glavnu osu, bez vršnog zadebljanja. Testovi patogenosti uključili
su inokulacije mladih biljaka I. walleriana prskanjem suspenzijom sporangija, a simptomi
plamenjače razvili su se nakon 13-15 dana. Odsustvo definisanih pega na zaraženim listovima
impatiensa i prisustvo pravih sporangiofora ukazalo je da je prouzrokovač P. obducens,
što je dalje potvrđeno molekularnom identifikacijom. Primenom lančane reakcije
polimeraze (polymerase chain reaction, PCR), pomoću prajmera NL1 i NL4, umnožen
je kodirajući 5’-kraj DNA velike ribozomalne podjedinice (LSU rDNA). Amplifikovani produkt
odabranog izolata 28-10 je sekvencioniran, a filogenetske analize pokazale su njegovo
grupisanje sa ostalim izolatima P. obducens različitog porekla. Uzimajući u obzir da
je ovim istraživanjima dokazano da je prouzrokovač plamenjače na Impatiens walleriana
u Srbiji P. obducens, neophodno je preduzimanje odgovarajućih fitosanitarnih mera u cilju
sprečavanja daljeg širenja patogena u našoj zemlji.