Carvalho, Susana M. P.

Gallego, Pedro P.

Santos, Miguel G.

Silva, Marta Nunes da

Vasconcelos, Marta W.

English

Repositório Institucional da Universidade Católica Portuguesa

▪ [C] – mock-inoculation with Ringer´s solution (control);▪ [BAG] – Plant enclosure in plastic transparent bag for 24 h before and 24 h after inoculation;▪ [CUTS] – Leaf wounding with three superficial cuts with a blade;▪ [COLD] – Plant maintained at 5 ºC for 24 h before inoculation;▪ [ALL] – Combination of all procedures above.Assessing the effectiveness of different Pseudomonas syringae pv. actinidiae pre-inoculation procedures to promoting disease visual symptoms in adult kiwifruit plantsMiguel G. Santosa, Marta Nunes da Silvab, Pedro P. Gallegoc, Marta W. Vasconcelosb and Susana M. P. Carvalhoa*aGreenUPorto – Sustainable Agrifood Production Research Centre / Inov4Agro, DGAOT, Faculty of Sciences of the University of Porto, Campus de Vairão, Rua da Agrária 747, 4485-646 Vila do Conde, Portugal bCentro de Biotecnologia e Química Fina – Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Diogo Botelho 1327, 4196-005 Porto, Portugal cPlant Biology and Soil Science Department, Faculty of Biology of the University of Vigo, 36310 Vigo, Spain*Corresponding author: susana.carvalho@fc.up.pt▪ In planta experiments under laboratory and field conditions, basedon artificial Psa inoculations, follow different procedures.▪ Most utilized methods of Psa artificial inoculation includeinduction of plant physiological stress, plant wounding andpromoting bacterial entrance through natural openings andfavoring the environmental conditions for Psa colonization (e.g.,humidity).IntroductionObjectiveMaterials & methodsResults and discussionConcluding remarksAcknowledgements This work was financed by national funds from the Foundation for Science and Technology (FCT) through the Ph.D. scholarship of Miguel G. Santos (2020.08874.BD) and within the scope of UID/Multi/50016/2019, UIDB/05748/2020 and UIDP/05748/2020. ▪ The bacterium Pseudomonas syringae pv. actinidiae (Psa) is theaetiological agent of Kiwifruit Bacterial Canker (KBC).▪ Worldwide pandemic after successive outbreaks since 2008;▪ Disease with greatest impact on the kiwifruit (Actinidia spp.1)industry.▪ Assess the effectiveness of Psa pre-inoculation procedures in termsof promoting Psa capacity to cause disease visual symptoms.▪ Testing four pre-inoculation procedures in adult kiwifruit plantsartificially inoculated with Psa.▪ A. chinensis var. deliciosa ‘Tomuri’ plants (6-months old);▪ Grown in 2.5 L pots with peat-based substrate mixed withperlite (3:1 v/v);▪ Grown in a climate chamber for 21 days after Psa-inoculation;▪ Four plants (n = 4) per treatment.▪ Inoculum of Psa strain CFBP7286 (107 CFU/mL) prepared inRinger´s solutions.1 Commercial cultivars belong to the species A. chinensis (var. deliciosa and var. chinensis) and A. arguta (kiwiberry).Pre-inoculation procedures▪ The pre-inoculation procedure influences Psa colonization, subsequently affecting the ability of the bacteria to cause KBC symptoms in kiwifruit.    ▪ The results from this study indicate that cautious should be taken when comparing Psa pathogenicity between studies where different (pre-)inoculation procedures have been adopted. ▪ This work highlights the importance of following optimum procedures of plant artificial inoculation in phytopathology research studies.▪ Treatment BAG strongly increased the capacity of Psa to causevisual symptoms.▪ Plants from BAG showed 7 times more leaf spots than plantsfrom all pre-inoculation procedures combined (ALL).▪ Maintenance of high-humidity in BAG most likely promotedstomatal aperture → natural opening for colonization.AssessmentPsainoculationMock-inoculation▪ Visual symptoms → number of spots per leaf. 5 °C 5 °Cinoculation▪ Psa colonizes the hosts mainly through natural openings andwounds (e.g., pruning cuts), rapidly reaching the xylem and phloem→ systemic▪ Main disease symptoms:▪ Favorable environmental conditions to Psa spread:▪ Mild temperatures, high relative humidity, hail and frost events.Leaf spottingCanker formationTwig and cane dieback▪ Except for treatment BAG, no other pre-inoculation procedurewas effective in causing KBC symptoms → no significantdifference when compared to the control.▪ Despite showing No. of spots per leaf ranging from 4.4(COLD) to 24.9 (ALL) → high variation coefficient, in general.▪ Use of low temperature (COLD) and leaf cutting (CUTS) maynot be suitable pre-inoculation procedures to promote Psainfection → they may have diminished the efficacy of usingbag enclosure, causing low symptom appearance in ALL.Spraying 10 mL of inoculum solution C BAG CUTS COLD ALLbab bb050100150200250300C BAG CUTS COLD ALLNo. of spots per leafPre-inoculation procedure

Assessing the effectiveness of different Pseudomonas syringae pv. actinidiae pre-inoculation procedures to promoting disease visual symptoms in adult kiwifruit plants

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Assessing the effectiveness of different Pseudomonas syringae pv. actinidiae pre-inoculation procedures to promoting disease visual symptoms in adult kiwifruit plants

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