Control of fire blight (Erwinia amylovora) on apple trees with trunk-injected plant resistance inducers and antibiotics and assessment of induction of pathogenesis-related protein genes

Abstract

Management of fire blight is complicated by limitations on use of antibiotics in agriculture, antibiotic resistance development, and limited efficacy of alternative control agents. Even though successful in control, preventive antibiotic sprays also affect non-target bacteria, aiding the selection for resistance which could ultimately be transferred to the pathogen Erwinia amylovora. Trunk injection is a target-precise pesticide delivery method that utilizes tree xylem to distribute injected compounds. Trunk injection could decrease antibiotic usage in the open environment and increase the effectiveness of compounds in fire blight control. In field experiments, after 1–2 apple tree injections of either streptomycin, potassium phosphites (PH), or acibenzolar-S-methyl (ASM), significant reduction of blossom and shoot blight symptoms was observed compared to water injected control trees. Overall disease suppression with streptomycin was lower than typically observed following spray applications to flowers. Trunk injection of oxytetracycline resulted in excellent control of shoot blight severity, suggesting that injection is a superior delivery method for this antibiotic. Injection of both ASM and PH resulted in the significant induction of PR-1, PR-2, and PR-8 protein genes in apple leaves indicating induction of systemic acquired resistance (SAR) under field conditions. The time separating SAR induction and fire blight symptom suppression indicated that various defensive compounds within the SAR response were synthesized and accumulated in the canopy. ASM and PH suppressed fire blight even after cessation of induced gene expression. With the development of injectable formulations and optimization of doses and injection schedules, the injection of protective compounds could serve as an effective option for fire blight control.

Los fosfitos como alternativa para el manejo de problemas fitopatológicos

“…El ion fosfito es fácilmente transportado en las plantas vía xilema y floema (McDonald et al, 2001;Tkaczyk et al, 2016), por lo que se ha utilizado en aplicación foliar (Rebollar-Alviter et al, 2010;Silva et al, 2011;Pagani et al, 2014;Yáñez et al, 2014;Liljeroth et al, 2016;Borza et al, 2017), baño a la raíz y cuello de la planta (Oka et al, 2007;Akinsanmi y Dreth, 2013), inyección al tronco (Bock et al, 2012;Akinsanmi y Drenth, 2013: Aćimović et al, 2015Aćimović et al, 2016), a través de riego por goteo mezclado en la solución nutritiva en hidroponía (Förster et al, 1998), tratamiento a semilla (Abbasi y Lazarovits 2006; Lobato et al, 2008), aplicación aérea en bajo volumen ) o como tratamiento en inmersión de semillas y frutos (Anderson et al, 2012;Cerioni et al, 2013, Borin et al, 2017Pagani et al, 2014;Yáñez et al, 2014;Liljeroth et al, 2016;Borza et al, 2017), drench of plants root and neck (Oka et al, 2007;Akinsanmi and Dreth, 2013), trunk injection (Bock et al, 2012;Akinsanmi andDrenth, 2013: Aćimović et al, 2015;Aćimović et al, 2016) through drip irrigation mixed in a nutrient solution in hydroponics (Förster et al, 1998), seed treatments (Abbasi and Lazarovits 2006; Lobato et al, 2008), low-volume aerial applications or as a treatment in seed and fruits immersion (Anderson et al, 2012;Cerioni et al, 2013, Bor...…”

Choosing an Adequate Pesticide Delivery System for Managing Pathogens with Difficult Biologies: Case Studies onDiplodia corticola, Venturia inaequalisandErwinia amylovora

“…Agricultural, urban, and natural tree stands have been the focus of extensive plant pathogen diagnostic and disease management research in recent decades [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] which recorded an increase in the number of new fungal and bacterial pathogens and their detrimental impact on agroecosystems, ecosystems, and the human society. The economic effects of these pathogens are reflected in lost fresh fruit produce [17][18][19], reduced yields and quality of fruit or wood and cork products [20,21], diminished ecological tree services, and death of whole trees, stands, and forest regions or decimation of fruit industries [19,22].…”

“…To achieve delivery of an effective pesticide dose, its distribution and expected management of plant detrimental organism or nutrient deficiency, there are several key factors which should be monitored by an applicator as they influence success of trunk injection for these purposes. Besides the plant pathogen biology, ecology, and epidemiology, several factors play a key role in success of trunk injection efficacy: the time of application in relation to detrimental organism establishment and symptom occurrence [11], the season and time of the day of application [41], the chemical properties of pesticide active ingredient and its formulation [42], the injected volume or dose of a pesticide, and the type of tree injection device or technology. For example, a more effective management of plant disease or insect infestation can be achieved by the preventive injections of pesticides in comparison to the therapeutic pesticide applications after the disease or infestation has already occurred.…”

“…avocado thrips, Scirtothrips perseae; Phytophthora root rot, Phytophthora cinnamomi) [49,50], apple (e.g. fire blight, Erwinia amylovora; apple scab, V. inaequalis [11,12]; oblique banded leaf roller, Choristoneura rosaceana [10,52]), and grapevine (e.g. grapevine downy mildew, Plasmopara viticola [53]; powdery mildew, Uncinula necator [54]).…”

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“…Lately, the rediscovered and rehabilitated colistin was considered as a final trump (Kádár et al, 2013) until colistin resistance was found in Gram-negative bacterium species, (Otter et al, 2017). Antibiotics are also used in plant medicine (Mc Manus et al, 2002;Stockwell, Sundin and Jones, 2002;Aćimović et al, 2015), but the increasing number of streptomycin-resistant Erwinia amylovora isolates has been causing serious problems both in the USA (Förster et al, 2015) and in Europe (Gusberti et al, 2015).…”