Palacký
University, Faculty of Science, Department of Botany, 783 71 Olomouc-Holice,
Czech Republic
Paradižnikova
pepelovka (Oidium lycopersici) je pritegnila pozornost fitopatologov in žlahniteljev
že pred več kot 10 leti, ko je prišlo zaradi nje do epifitocije na paradižniku.
Gliva je nevaren patogen in se je razširila v zmerno toplem območju starega in
novega Sveta. Njen izvor ni natančno znan (verjetno pa gre za mutacijo neznane
vrste). Doslej so bile raziskave usmerjene predvsem k morfološkim značilnostim
glive, vrstam gojiteljskih rastlin in k izvoru odpornosti znotraj rodu Lycopersicum
(vključujoč raziskave obrambnih mehanizmov osnov odpornosti). Vendar pa je
dosegljivo malo podatkov o biologiji patogena in o znotraj vrstnih razlikah. V
tem prispevku predstavljamo novejše podatke o patogenu s poudarkom na lastnih
raziskavah. V prispevku je osvetljena problematika identifikacije patogena.
Zaradi odsotnosti teleomorfnega stadija je bila otežkočena natančna
taksonomska uvrstitev glive. Zadnje raziskave, ki vključujejo primerjalna
morfološka opazovanja in genetske analize, kažejo na to, da je mogoče O. lycopersici uvrstiti v Erysiphe
sect. Erysiphe in da je skoraj identična
z Erysiphe aquilegiae var. ranunculi.
Iskanja divjih vrst Lycopersicon,
odpornih za O. lycopersici, so
razkrila dragocene izvire odpornosti, večinoma med L.
hirsutum in L. pennellii (kar so
potrdila testiranja s štirimi različnimi izolati O. lycopersici). Ugotovljena pa je bila tudi velika občutljivost za
L. esculentum var. cerasiforme
in L. pimpinellifolium. V okviru raziskav gostiteljev smo razen
alternativnih gostiteljev za Oidium
lycopersici ugotovili visoko stopnjo variabilnosti glede patotipov (formae
specialis). Druge raziskave pa so pokazale, da so izolati vrste O.
lycopersici različno patogeni za gostiteljske rodove in/ali vrste. Med
kultivarji in linijami Lycopersicum
esculentum niso našli signifikantnih razlik v odpornosti za O.
lycopersici zaradi njegove velike občutljivosti. V prispevku navajamo prve
jasne dokaze za pojav rasne specifičnosti v interakcijah divjih Lycopersicum
vrst – O. lycopersici in za
obstoj ras pri glivi O. lycopersici.
Navajamo tudi mehanizme in podlage za odpornost pri Lycopersicum spp. V bodoče bo potrebno pospešiti tovrstne
raziskave s klasičnimi, biokemijskimi in molekulskimi metodami.
ABSTRACT
Tomato
powdery mildew (Oidium lycopersici) has attracted the attention of plant
pathologists and breeders for more than 10 years, since it started
to cause epidemics on tomato. It is dangerous pathogen which spreaded
through temperate areas in the Old
and New Worlds, and which origin
is not exactly known (probably
mutation of unknown species). Till now the experimental studies were
concentrated mainly on morphological
characterization of this pathogen, host range and searching for resistance
sources within genus Lycopersicon (including
study of defence mechanisms and basis of resistance). However, less data is available on biology of this pathogen and its
intraspecific variation. Authors in their contribution summarized recent
information on this pathogen, with emphasis on their own experimental data.
In survey are enlighted
problems of pathogen identification, because absence of teleomorph stage did not
allow its exact taxonomic classification. Recent studies, including comparative
morphological observations and genetical analysis, show
that O. lycopersici
can be referred to Erysiphe sect. Erysiphe
and it is nearly identical to Erysiphe
aquilegiae var. ranunculi.
Screening of wild Lycopersicon spp.
for resistance to O. lycopersici
revealed valuable sources of resistance, mainly among L. hirsutum and L. pennellii
(confirmed by testing with four different O.
lycopersici isolates), opposite to high susceptibility recorded in L.
esculentum var. cerasiforme and L.
pimpinellifolium. Host range studies, besides detecting of some alternative
hosts of Oidium lycopersici, showed high
intraspecific variability on the level of pathotypes (formae
speciales). Other studies confirmed that O.
lycopersici isolates may also differ in pathogenicity within one plant genus
and/or species. Among Lycopersicon
esculentum cultivars and lines there was not found significant variation for
resistance to O. lycopersici, because
of their high susceptibility. However, authors give the first clear evidence
about phenomenon of race-specificity in interaction wild Lycopersicon
spp. - O. lycopersici and
existence of tomato powdery mildew races. Information regarding recently
detected mechanisms and basis of resistance in Lycopersicon spp. is also mentioned. However, more research based on
classical, biochemical and molecular approaches is needed.