Plant volatiles cause direct, induced and associational resistance in common bean to the fungal pathogen Colletotrichum lindemuthianum

Abstract

Experimental Baj ıo, INIFAP-Celaya, Km 6.5 Carr. Celaya-San Miguel de Allende 38810, Guanajuato, M exico Summary 1. Plants that express resistance to herbivores emit volatile organic compounds (VOCs) that can trigger resistance responses in undamaged neighbours. Recent reports indicate that VOCs can also trigger the resistance to pathogens, an effect that might be due to different mechanisms: the priming of an induced expression of resistance genes in the receiver or direct inhibitory effects on microbial pathogens that cause a passive 'associational' resistance in the VOC-exposed plant. 2. We investigated whether VOCs emitted from a resistant common bean (Phaseolus vulgaris) cultivar enhance the resistance to the fungus Colletotrichum lindemuthianum in a susceptible cultivar and analysed whether specific VOCs are likely to directly affect the pathogen. 3. We found that susceptible plants exposed to the headspace of resistance-expressing plants over 6 h became phenotypically as resistant as the resistant cultivar. Several resistance marker genes (PATHOGENESIS-RELATED [PR] 1, 2 and 4) were primed in VOC-exposed susceptible plants. After challenging, these genes reached expression levels at least as high as in the resistant cultivar. Additionally, individual VOCs such as limonene, linalool, nonanal, methyl salicylate and methyl jasmonate at natural concentrations directly inhibited the germination of conidia as did also the headspace of a resistance-expressing plant. This inhibition of conidial germination was dosagedependent and irreversible. 4. Synthesis. We conclude that VOCs are involved in the resistance of bean to fungal pathogens. They can contribute to the direct resistance in the emitter itself, and resistance phenotypes of neighbouring receiver plants can result from induced as well as associational resistance. Plant VOCs play multiple roles in the resistance of plants to microbial pathogens.

Herbivore intoxication as a potential primary function of an inducible volatile plant signal

“…; Quintana‐Rodriguez et al . ), both of which may provide direct fitness benefits to herbivore‐attacked plants without the need of HIPV perception by another organism. The sesquiterpene ( E )‐(β)‐caryophyllene, for instance, reduces flower colonization by the bacterial pathogen Pseudomonas syringae pv.…”

Identification of a Dolabellane Type Diterpene Synthase and other Root-Expressed Diterpene Synthases in Arabidopsis

“…This diversity is reflective of the multiple biological roles of terpene compounds in the attraction of pollinators (Byers et al, 2014), in direct and indirect defense against herbivores and pathogens (Kessler and Baldwin, 2001; Unsicker et al, 2009; Hall et al, 2011; Schmelz et al, 2011; Huang et al, 2012; Mithöfer and Boland, 2012; Quintana-Rodriguez et al, 2015), as signals in systemic acquired resistance or inter/intra-plant communication (Arimura et al, 2000; Heil and Silva Bueno, 2007; Karban and Shiojiri, 2009; Chaturvedi et al, 2012), and in the protection against abiotic stress (Loreto et al, 2001; Ryan et al, 2014; Vaughan et al, 2015). To facilitate such interactions at short and long distance, plants often employ volatile or semi-volatile terpenes of low molecular weight that include the 5-carbon hemiterpenes, 10-carbon monoterpenes, 15-carbon sesquiterpenes, and 20-carbon diterpenes (Dudareva et al, 2006).…”

Emission of volatile sesquiterpenes and monoterpenes in grapevine genotypes following Plasmopara viticola inoculation in vitro

“…Several studies have characterized the production of plant VOCs in response to herbivore attack and demonstrated the role of VOCs in the defense mechanisms, both by directly deterring herbivores and by attracting their predators . VOCs are also emitted by plants in response to pathogen infection, and they typically consist of green leaf volatiles, terpenoids, methyl jasmonate (MeJA), methyl salycilate (MeSA), aldehydes, and terpenes . However, little is known about the role of these VOCs in the defense mechanisms against pathogens .…”