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

2014; Wiley; Volume: 103; Issue: 1 Linguagem: Inglês

10.1111/1365-2745.12340

1365-2745

Elizabeth Quintana-Rodríguez, Adán Topiltzin Morales-Vargas, Jorge Molina‐Torres, Rosa M. Ádame‐Alvarez, Jorge Alberto Acosta Gallegos, Martin Heil,

Plant Pathogens and Fungal Diseases

Summary Plants that express resistance to herbivores emit volatile organic compounds ( VOC s) that can trigger resistance responses in undamaged neighbours. Recent reports indicate that VOC s 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. We investigated whether VOC s 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 VOC s are likely to directly affect the pathogen. 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 VOC s 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 dosage‐dependent and irreversible. Synthesis . We conclude that VOC s 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 VOC s play multiple roles in the resistance of plants to microbial pathogens.