Skip to main content
Doctoral thesis, 2013

Studies of plant interactions with other organisms to understand Bacillus mediated stress management

Johansson, Anna


The naturally evolved plant defense system is not always effective, due to adaptations among the attackers. Crop protective chemicals have many negative effects on the environment. Ecosystem services, like beneficial microorganisms, are of great interest for plant stress management in sustainable crop production. In this study, the rhizobacterium Bacillus amyloliquefaciens, known to protect oilseed rape (Brassica napus) to fungal diseases, was investigated. The aims were to test whether stains of Bacillus could protect oilseed rape against insect herbivores, and to find out more about factors involved in plant defense and Bacillus mediated stress protection. Depending on the mode of treatment B. amyloliquefaciens were able to protect oilseed rape plants against feeding by the generalist herbivore Spodoptera littoralis. Analysis of transcripts and hormones implied involvement of JA signaling in Bacillus interaction with oilseed rape, and metabolomic fingerprinting indicated special responses to the Bacillus treatment. Real-time PCR (qPCR) assays were developed for the closely related B. amyloliquefaciens strains UCMB5033, UCMB5036 and UCMB5113. Using this, we revealed that mainly roots are colonized, and we saw a genotype dependence of colonization and growth promotion efficiency on two oilseed rape cultivars. A test with feeding by one generalist and one specialist herbivore on gene silenced (virus-induced) and mutant Arabidopsis thaliana plants, revealed a complex role of the MD2-related lipid recognition (ML3) gene in defense signaling, affecting both jasmonic acid (JA) and salicylic acid (SA) associated responses. The plant protective ability of Bacillus was investigated using A. thaliana Col-0 and An-1, and differential disease suppression was found against a broad spectrum of pathogens but no mediated protection against a specialist herbivore. Analyses of defense genes, hormone levels and mutants indicated that UCMB5113 was capable of activating both SA and JA defense, dependent on NPR1. Overall, the studies carried out revealed some mechanism of Bacillus mediated priming of plant defense, involving resource allocation as part of a less costly defense strategy.


Bacillus amyloliquefaciens; Oilseed rape; Arabidopsis; ISR

Published in

Acta Universitatis Agriculturae Sueciae
2013, number: 2013:42
ISBN: 978-91-576-7823-2, eISBN: 978-91-576-7823-2
Publisher: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences

Authors' information

Johansson, Anna
Swedish University of Agricultural Sciences, Department of Plant Biology

UKÄ Subject classification

Agricultural Science

URI (permanent link to this page)