title: Organic amendments to avocado crops induce suppressiveness and influence the composition and activity of soil microbial communities.
abstract: One of the main avocado diseases in southern Spain is white root rot caused by the fungus Rosellinia necatrix Prill. The use of organic soil amendments to enhance the suppressiveness of natural soil is an inviting approach that has successfully controlled other soilborne pathogens. This study tested the suppressive capacity of different organic amendments against R. necatrix and analyzed their effects on soil microbial communities and enzymatic activities. Two-year-old avocado trees were grown in soil treated with composted organic amendments and then used for inoculation assays. All of the organic treatments reduced disease development in comparison to unamended control soil, especially yard waste (YW) and almond shells (AS). The YW had a strong effect on microbial communities in bulk soil and produced larger population levels and diversity, higher hydrolytic activity and strong changes in the bacterial community composition of bulk soil, suggesting a mechanism of general suppression. Amendment with AS induced more subtle changes in bacterial community composition and specific enzymatic activities, with the strongest effects observed in the rhizosphere. Even if the effect was not strong, the changes caused by AS in bulk soil microbiota were related to the direct inhibition of R. necatrix by this amendment, most likely being connected to specific populations able to recolonize conducive soil after pasteurization. All of the organic amendments assayed in this study were able to suppress white root rot, although their suppressiveness appears to be mediated differentially.
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora," Universidad de Málaga, Consejo Superior de Investigaciones Científicas, and Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Bonilla
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora," Universidad de Málaga, Consejo Superior de Investigaciones Científicas, and Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Vida
authors.affiliation: Departamento de Genética y Microbiología, Facultad de Biociencias, Universidad Autónoma de Barcelona, Bellaterra, Spain.
authors.forename: Maira
authors.initials: M
authors.lastname: Martínez-Alonso
authors.affiliation: Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas, Finca Alameda del Obispo, Córdoba, Spain.
authors.forename: Blanca B
authors.initials: BB
authors.lastname: Landa
authors.affiliation: Departamento de Genética y Microbiología, Facultad de Biociencias, Universidad Autónoma de Barcelona, Bellaterra, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Gaju
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora," Universidad de Málaga, Consejo Superior de Investigaciones Científicas, and Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Cazorla
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora," Universidad de Málaga, Consejo Superior de Investigaciones Científicas, and Departamento de Microbiología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain adevicente@uma.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: de Vicente
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D064307:Microbiota; D008969:Molecular Sequence Data; D058871:Organic Agriculture / Q000295:instrumentation / Q000379:methods*; D027421:Persea / Q000254:growth & development / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology; D012988:Soil Microbiology; D013098:Xylariales / Q000502:physiology*