Johanna Witzell

Phytophthora Citizen Science researcherPresentation

Associate professor, Editor-in-Chief Scandinavian Journal of Forest Research


I have given lectures in subjects related to forest damages and diseases, tree resistance and defense against natural enemies, and chemical ecology (SLU Umeå and Alnarp, UmU, Lund Univ.). During my recent affiliation with UEF in Finland (2014-2016), I was course leader for MSc level courses 3513143 “Microbes in trees and wood” (5 ECTS), 3513142 “Basics of wood materials science” (1 ECTS), 3513138 “Thesis Seminar II in Wood Materials Science” (1 ECTS), 3513139 “Master’s Thesis in Wood Materials Science” (30 ECTS). I have organized several PhD courses as a research school coordinator (2008-2013).


Photo: Johanna Witzell

My research interests are forest damages, tree resistance and stress responses (with special interest in phenolic defensive compounds), functional traits of fungal endophytes of trees, Dutch elm disease and invasive Phytophthora-species. I am interested in the interface between biology and forest management, e.g., how fertilization influences tree quality, how thinning influences fungal biodiversity, or how the fungal communities can influence tree resistance or regeneration success. My current research is financed by Swedish Research Council Formas and Crafoord foundation. I currently collaborate with Dr. Michelle Cleary (SLU; Phytophthora-damages of broadleaved trees), Assoc. Prof. Benedicte Albrectsen (Umeå University, Umeå Plant Science Center; endophytes and tree chemical defenses), Prof. Juan A. Martín (UPM, Madrid, Spain; Dutch elm disease, tree endophytes), Prof. Olov Sterner (Lund University; analysis of fungal chemicals), Docent Tarja Lehto (UEF, Finland; functional characteristics of northern forest trees) and Dr. Dan Bergström and Prof. Urban Bergsten (SLU; effects of thinning regimes on biodiversity).


Chemical defense of trees, based on phenolic metabolites, has been the subject of most my studies since I finished my PhD in Professor Riitta Julkunen-Tiitto’s (UEF, Finland) research group in Finland (1998). My PhD thesis focused on studying the effect of nitrogen fertilization on the growth and phenolic metabolites in dark-leaved willow (Salix myrsinifolia Salisb.). After that, I worked as a post-doctoral fellow in Professor Alan Slusarenko’s laboratory (RWTH Aachen, Germany) where I had a possibility to learn more about the defensive mechanisms in the model plant Arabidopsis.

I came to Sweden in 1999 to work as a post-doctoral fellow in Professor Torgny Näsholm’s group (SLU, Umeå Plant Science Center). In that position, I continued to explore the effects of nitrogen amendments on plant defensive chemistry, but this time the study system was bilberry (Vaccinium myrtillus L.), a keystone species of boreal forests. Between 2002 and 2006, I continued this research an assistant professor, financed by the Swedish Research Council Formas.

In 2006, I moved to Southern Swedish Forest Research Center, where I started to work with Dutch elm disease (collaboration with Prof. Juan A. Martín, UMP Madrid), focusing on the role of endophytic communities in this disease complex. Since 2010, I have also been working with Phytophthora-damages of broadleaved trees, lately in close collaboration with Dr. Michelle Clearly, who recently joined our department and is now leading this line of research. This work includes close contacts with forest owners and common public. Together with Professor Urban Bergsten (SLU Umeå), I coordinated a research school “Sustainable Management and Utilization of Forests” in 2008-2013.

During 2014-2016, I was holding a chair of Professor in Wood Materials Science at my Alma mater, the University of Eastern Finland (80% of full time). My main task in this position was to lead the international MSc program in Wood Materials Science. Since June 2016, I am back at SLU where I continue research on forest tree health and I am also leading a new research school “Bio-economy adapted forest management”, which is a collaboration with several Swedish forest companies and The Faculty of Forest Sciences at SLU.


I was main supervisor for Dr. Kathrin Blumenstein who defended her thesis in December 2015. I am currently main supervisor for Marta Agostinelli, who will defend her thesis in 2017. In addition, I am co-supervisor for three PhD students (Mattias Engman and Adrian Villalobos at SLU, and Taru Koskinen at UEF, Finland). I have been co-supervisor for four completed PhD students in 2005-2013. I have supervised several BSc and MSc thesis projects.

Some of the publications

Cleary M, Ghasemkhani M, Blomquist M, Witzell J. (2016) First report of Phytophthora gonapodyides causing disease of European beech (Fagus sylvatica) in Southern Sweden. Plant Disease (in press). 

Anderbrant O, Yuvaraj JK, Martin JA, Gil L, Witzell J (2016) Feeding by Scolytus bark beetles to test for differently susceptible elm varieties. Journal of Applied Entomology (in press).

Romeralo C, Witzell J, Diez JJ (2016) Aleppo pine provenances vary in susceptibility and secondary chemical response to Gremmeniella abietina infectionPlant Pathology (in press).

Kaitera J & Witzell J (2016). Phenolic profiles of two Melampyrum species differing in susceptibility to Cronartium rustEuropean Journal of Plant Pathology 144: 133-140.

Romeralo C, Witzell J, Romeralo-Tapia R, Botella L & Diez J (2015). Antagonistic activity of fungal endophyte filtrates against Gremmeniella abietina infections on Aleppo pine seedlingsEuropean Journal of Plant Pathology 143: 691-704. 

Blumenstein K, Macaya Sanz D, Martín JA, Albrectsen BR & Witzell J (2015) Phenotype Microarrays as a complementary tool to next generation sequencing for characterization of tree endophytesFrontiers Microbiology 6:1033.

Gunulf A, Witzell J and Rönnberg J (2015). Risk of false positives during sampling for Heterobasidion annosum s.l. Plant Disease 100: 175-179. 

Martín JA, Macaya-Sanz D, Witzell J, Blumenstein K, Gil L (2015). Strong in vitro antagonism by elm xylem endophytes is not accompanied by temporally stable in planta protection against a vascular pathogen under field conditions. European Journal of Plant Pathology 142: 185-196.

Blumenstein K, Albrectsen B, Martín JA, Hultberg M, Sieber T, Helander M, Witzell J (2015) Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease. BioControl 60: 655-667.