Strategije nadzora nad metličavostjo jablan, resno boleznijo, ki se pojavlja tako v Italiji kot tudi v  Sloveniji  

Ruggero OSLER1, Nataša PETROVIČ2, Paolo ERMACORA3, Gabrijel SELJAK4, Jernej BRZIN5, Nazia LOI6, Luigi CARARRO7, Francesca FERRINI8, and Elvio REFATTI9

  1,3,6,7,8,9 Universita' degli studi di Udine, Dipartimento di Biologia Applicata alla Difesa delle Piante, IT-33100 Udine, Italija
2,5 Nacionalni inštitut za biologijo, Oddelek za rastlinsko fiziologijo in biotehnologijo, SI-1000 Ljubljana, Slovenija
4 Kmetijsko veterinarski zavod, SI-5000 Nova Gorica, Slovenija

   

Metličavost jablan (AP) je resna bolezen, ki večinoma napada jablane. Povzroča jo fitoplazma, ki je razširjena po Evropi, predvsem pa po Južni Evropi. V zadnjem času poročajo o epidemijah te bolezni v Severni Italiji, predvsem na kultivarjih zlati delišes, florina, kanadska reneta in Granny Smith, cepljenih na različne podlage. Tudi v Sloveniji smo v zadnjem času opazili večjo razširjenost te bolezni. Tudi novi genotipi jablan, odpornih na jablanov škrlup, ki so jih vzgojili iz Malus floribunda, kažejo občutljivost na metličavost. Slaba kakovost sadja postavi pridelovalne nasade v ekonomsko neugoden položaj. Na področju Furlanije v Severni Italiji lahko odstotek dreves z izraženimi bolezenskimi znamenji v posameznih nasadih preseže 50%. Na splošno velja, da lahko posamezna okužena drevesa v odvisnosti od okolja, kultivarja in kmetijske prakse izgubijo bolezenska znamenja (angl. 'recovered' , slov. 'okrevali') in dajejo pričakovani pridelek. V nekaterih primerih lahko taka 'okrevala' drevesa normalno obrodijo sadeže dobre kakovosti. O bolezni poročajo tudi iz drevesnic, v katerih se lahko okužijo sejanci s cepljenjem ali pa z naravnimi prenašalci. Ne glede na način prenosa bolezni, nas takšna situacija postavi pred velik in zapleten problem. V naravi fitoplazmo metličavosti prenašata  dve vrsti bolšic (Cacopsylla costalis in C. melanoneura), zaradi njene sistemske razporejenost v gostiteljskih rastlinah pa je možen tudi prenos s cepljenjem. Naravni ciklus metličavosti in njenih prenašalcev je v grobem znan. Na voljo so občutljive in zanesljive diagnostične metode kot na primer nespecifična tehnika z barvanjem DAPI ter serološke in molekularno-biološke metode. V praksi je okužena drevesa nemogoče popolnoma ozdraviti.

Postopki za preprečevanje okužbe v glavnem temeljijo na poznavanju epidemiologije AP. Najpomembnejši postopki zajemajo: uporabo testiranega sadilnega materiala v novih pridelovalnih nasadih, uporabo šibkih podlag, izogibanje občutljivim sortam, pridobivanje odpornih/tolerantnih genotipov, postavljanje drevesnic v območja, kjer bolezni ni ter izogibanje sadilnemu materialu, ki prihaja iz okuženih območij. Kadar pa že imamo opravka z epidemijo, so načini zatiranja bolezni: uporaba insekticidov, izkop predvsem v zgodnji fazi epidemije, izkoriščanje pojava 'recovery', uporaba apomiktičnih podlag odpornih na AP, izogibanje močni rezi, vzdrževanje dreves v uravnoteženi rasti, izogibanje sajenju občutljivejših mladih dreves na epidemična področja, predvsem tam, kjer so pred kratkim izkopali okužena drevesa.

   

 

ABSTRACT

Control strategies of Apple proliferation, a serious disease occuring both in Slovenia and in Italy

 

Apple proliferation (AP) is a serious disease that mainly affects apple-trees. It is caused by a phytoplasma diffused in Europe, particularly in the South. Recently, serious epidemics have been reported to occur in northern Italy, particularly on cvs Golden Delicious, Florina, Canadian Renette and Granny Smith, grafted on different rootstocks. The disease was found to be in progress also in Slovenia. Also the new genotypes resistant to scab and derived from Malus floribunda are susceptible to AP. Because of the poor quality of fruits, the infected orchards easily became economically not convenient. In Friuli-V.G., the percentage of symptomatic trees in an infected orchard can be easily over than 50%. In general, depending on the environment, cultivar and agronomic treatments the infected trees can recover from the symptoms and produce regularly. In some cases, the fruits produced by recovered trees are near to normal and of good quality. The disease has been recorded also in nurseries. In this case AP was transmitted to the young seedlings either by grafting or by natural vectors. In both cases a great and complicate problem arises. In nature the AP - agent is transmitted at least by two species of psylla (Cacopsylla costalis and C. melanoneura). AP is systemic in the host plant and it is transmitted also by grafting. The cycle of AP and of the natural vectors is roughly known. At present, we dispose of sensitive and reliable diagnostic techniques as: the use of DAPI staining, serology and molecular biology techniques. The disease is not possible to be practically cured.

Preventive procedures are on the contrary possible, mainly based on the knowledge of the epidemiology of AP. The most important and general prevention measures are as follows: utilize tested material when planting new orchards; use weak rootstocks; avoid the most sensitive cvs; obtain resistant/tolerant genotypes; establish nurseries in AP-non infected areas and avoid to use propagation material derived from infected areas. When operating in an already epidemic situation: vector control by using insecticides. Roughing especially during the initial phases of the epidemiology; take advantage of recovery; use of apomytic rootstocks resistant to AP; avoid heavy pruning or pollarding; keep the plants in vegetative balance; do not replace young sensitive plants in recently rouged orchards that are placed in infected areas still during the epidemic phase of the disease.