Role of the arbuscular mycorrhizal symbiosis in tolerance response against Armillaria mellea in lavender

Lavender species form the arbuscular mycorrhizal symbiosis and are at the same time highly susceptible to white root rot. In an attempt to evaluate the response of mycorrhizal Lavandula angustifolia L. to Armillaria mellea (Vahl:Fr) P. Kumm in a greenhouse experiment, plants were previously inoculated with an isolate of the arbuscular mycorrhizal fungus Rhizophagus irregularis (former Glomus intraradices BEG 72) and the influence of the pH growing medium on the plant-symbiont-pathogen interaction was tested in gnotobiotic autotrophic growth systems in which mycorrhizal inoculum was obtained from root organ cultures. After ten months growth dual-inoculated lavender plants grown in containers with a pasteurized substrate mixture produced a similar number of spikes than healthy plants and achieved equivalent plant diameter coverage. When the growing medium in the autotrophic systems was supplemented with calcium carbonate, the inoculation of lavender plantlets with R. irregularis at higher pH (7.0 and 8.5) media caused a significant decrease of A. mellea presence in plant roots, as detected by qPCR. Moreover, the observation of internal root mycorrhizal infection showed that the extent of mycorrhizal colonization increased in plant roots grown at higher pH, indicating that tolerance to white root rot in lavender plants inoculated with R. irregularis could be associated to mycorrhizal establishment. Additional key words: white root rot; control strategies; Glomus intraradices; Lavandula angustifolia; pH; Rhizophagus irregularis. Abbreviations used: AMF (arbuscular mycorrhizal fungi); MSR (Strullu-Romand medium); qPCR (real-time PCR); ROC (root organ culture). Citation: Calvet, C.; Garcia-Figueres, F.; Lovato, P.; Camprubi, A. (2015). Role of the arbuscular mycorrhizal symbiosis in tolerance response against Armillaria mellea in lavender. Spanish Journal of Agricultural Research, Volume 13, Issue 3, e1008, 8 pages. http://dx.doi.org/10.5424/sjar/2015133-7677. Received: 09 Mar 2015. Accepted: 07 Jul 2015 Copyright © 2015 INIA. This is an open access article distributed under the Creative Commons Attribution License (CC by 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Funding: Spanish Ministry of Economy and Competitiveness, MINECO (Grant AGL 2010-15017). Paulo Lovato was supported by Fundaçao Capes, Brazilian Ministry of Education. Competing interests: The authors have declared that no competing interests exist. Correspondence should be addressed to Cinta Calvet: [email protected]