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24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

Menu Logo Principal Plant pathology unit - INRA AVIGNON

Pathologie vegetale

Zone de texte éditable et éditée et rééditée


Research Director, Head of the MISTRAL research team



  • My research concerns bacterial ecology. My team seeks to understand how the adaptation of bacteria to their environment affects two seemingly conflicting impacts on the environment: their capacity to
    • cause disease, and in particular newly emerging diseases
    • play beneficial roles in major environmental phenomena.
  • The bacterium Pseudomonas syringae is the focus of our work. It is a recurring pathogen on a wide range of crops of major importance. The bacterium is also one of the most highly active, naturally occurring ice nucleators in the environment. Its ice nucleation activity - at temperatures warmer than most other ice nucleators - and its ability to ascend into clouds with air currents has solicited great interest in its possible role in the atmospheric processes that lead to rainfall.

Plant pathogens can reside is many habitats outside of agriculture as well as within and can move between these different habitats.  They can also have traits that are useful for their adaptation to all these different habitats and that lead them to play roles in a range of environmental phenomenon. For the bacterium Pseudomonas syringae, we study the influence of environmental habitats on the emergence of plant disease. We also study the dissemination of P. syringae via the water cycle and its influence on atmospheric processes that affect rainfall and lightning.

  • One of the long term goals of our work is to anticipate encounters of pathogenic strains of P. syringae from environmental reservoirs with crops and to identify the conditions most favorable for emergence. To accomplish this goal we :
    • identify the natural environmental reservoirs of P. syringae,
    • determine the role of these reservoirs in bacterial evolution,
    • assess the probability of dissemination to cultivated plants,
    • identify climatic factors most favorable for disease.
  • The other long term goal of our work is to contribute to land management strategies and policies that balance the dual roles of microorganisms that are plant pathogens and that are beneficial for rainfall. To accomplish this goal we :
    • identify sources of ice nucleation active microorganisms that are also plant pathogens,
    • evaluate the flux of these microorganisms from land covers to the atmosphere,
    • contribute to research on the role of microorganisms in cloud physics, including processes linked to rainfall, lightning and albedo,
    • assess and map the intensity of land-atmosphere feedbacks mediated by microorganisms.


  • Aho K., Weber C., Christner B., Vinatzer B., Morris C.E., Joyce R., Failor K., Werth J., Bayless‐edwards A., Schmale D. 2020. Spatiotemporal patterns of microbial composition and diversity in precipitation. Ecological monographs 90(1): e01394.
  • Šantl-Temkiv, T., Sikoparija, B., Maki, T., Carotenuto, F., Amato, P., Yao, M., Morris, C.E., Schnell, R., Jaenicke, R., Pöhlker, C., Demott, P.J., Hill, T.C.J., Huffman, J.A. 2020. Bioaerosol field measurements: Challenges and perspectives in outdoor studies. Aerosol Science and Technology 54: 520-546.
  • Morris C.E., Lamichhane J.R., Nikolić, I., Stanković S., Moury B. 2019. The overlapping continuum of host range among strains in the Pseudomonas syringae complex. BMC Phytopathology Research 1 :4
  • Morris C.E., Moury B. 2019. Revisiting the concept of host range of plant pathogens. Annu. Rev. Phytopathol. 57:63-90.
  • Omrani M., Roth M., Roch G., Blanc A., Morris C.E., Audergon J.M. 2019. Genome-wide association multi-locus and multi-variate linear mixed models reveal two linked loci with major effects on partial resistance of apricot to bacterial canker. BMC Plant Biol. 19 :31
  • Parisi L., Morgaint B., Blanco Garcia J., Guilbaud, C., Chandeysson C., Bourgeay J.-F., Moronvalle A., Bru, L., Brachet M. L., Morris C.E.  2019. Bacteria from four phylogroups of the Pseudomonas syringae complex can cause bacterial canker of apricot. Plant Pathology 68 :1249–1258.
  • Morris C.E. 2018. Phytobiomes contribute to climate processes that regulate temperature, wind, cloud cover and precipitation. Phytobiomes 2:55-6 1
  • Leyronas C., Morris C.E., Choufani M., Soubeyrand S. 2018. Assessing the aerial interconnectivity of distant reservoirs of Sclerotinia sclerotiorum. Frontiers in Microbiology, section Extreme Microbiology 9 :
  • Bardin M., Leyronas C., Troulet C., Morris C.E. 2018. Striking similarities between Botrytis cinerea from non-agricultural and from agricultural habitats. Frontiers in Plant Science, 9, 1820.
  • Carotenuto F., Georgiadis T., Gioli B., Leyronas C., Morris C. E., Nardino M., Wohlfahrt G., Miglietta F. 2017 Measurements and modeling of surface–atmosphere exchange of microorganisms in Mediterranean grassland. Atmos. Chem. Phys. 17, 14919-14936
  • Stopelli E., Conen F., Guilbaud C., Zopfi J., Alewell C., Morris C.E. 2017. Ice nucleators, bacterial cells and Pseudomonas syringae in precipitation at Jungfraujoch. Biogeosciences 14:1189-1196
  • Morris C.E., Soubeyrand S., Bigg E.K., Creamean J.M., Sands D.C. 2017. Mapping rainfall feedback to reveal the potential sensitivity of precipitation to biological aerosols. Bull. Amer. Meteorol. Soc., 98, 1109-1118.
  • Monteil C.L., Yahara K., Studholme D.J., Mageiros L., Méric G., Swingle B., Morris C.E., Vinatzer, B.A., Sheppard S.K. 2016. Population genomic insights into the emergence, crop-adaptation, and dissemination of Pseudomonas syringae pathogens. Microbial Genomics
  • Morris, C.E., Conen, F., Alex Huffman, J., Phillips, V., Pöschl, U., Sands, D. C. 2014. Bioprecipitation: a feedback cycle linking earth history, ecosystem dynamics and land use through biological ice nucleators in the atmosphere. Global change biology, 20 (2), 341-51.
  • Morris C.E., Monteil C.L., Berge O. 2013. The life history of Pseudomonas syringae: linking agriculture to Earth system processes. Annu. Rev. Phytopath. 51:85-104.


Christner B.C., Morris C.E., Foreman C.M., Cai, R., Sands D.C. 2008. Ubiquity of biological ice nucleators in snowfall. Science 319:1214.

Morris C.E., Monier J.-M. 2003. The ecological significance of biofilm formation by plant-associated bacteria. Annu. Rev. Phytopathol. 41:429-453.

Morris C.E., Sands D.C., Vinatzer B.A., Glaux C., Guilbaud C., Buffière A., Yan S., Dominguez H., Thompson B. 2008. The life history of the plant pathogen Pseudomonas syringae is linked to the water cycle. The ISME Journal, 2:321-334.

Ellison D., Morris C.E., Locatelli B., Sheil D., Cohen J., Murdiyarso D., Gutierrez V., van Noordwijk M., Creed I.F., Pokorny J., Gaveau D., Spracklen D., Bargués Tobella A., Ilstedt U., Teuling R., Gebrehiwot S.G., Sands D.C., Muys B., Verbist B., Springgay E., Sugandi Y., Sullivan C. 2017. Trees, forests and water: cool insights for a hot world. Global Environ. Change. 43 :51-61.