Arbuscular mycorrhizal fungi communities in citrus conventional and organic farming and their interactions with Phytophthora parasitica. / Comunidades de fungos micorrízicos arbusculares nos manejos convencional e orgânico de citros e suas interações com Phytophthora parasitica.

AUTOR(ES)

Soraya de Carvalho França

DATA DE PUBLICAÇÃO

2004

RESUMO

Farmers and technicians involved with organic citriculture try to develop systems with high microbial activity in soil. In this way, they expect to obtain benefits from processes that occur in soil, as natural control of pests and diseases. However, there are few studies about the influence of this type of management on soil microbiota, specially on the arbuscular mycorrhizal fungi (AMF) and the pathogen Phytophthora parasitica. The objectives of this thesis were: to evaluate mycorrhizal colonization and diversity of AMF in citrus conventional and organic farming; to evaluate benomyl application and γ radiation to obtain non-mycorrhizal controls for study of interaction between indigenous AMF and P. parasitica; to verify local and systemic capacity of indigenous AMF to induce resistance against P. parasitica; to study chitinase activity in roots of Rangpur lime colonized by indigenous AMF. Samplings were carried out in two citrus systems in São Paulo, one conventional and one organic farming. The richness and the diversity of AMF species were higher in the organic farming. In greenhouse, experiments with Rangpur lime (Citrus limonia) showed that γ radiation was better than benomyl to obtain non-mycorrhizal control for studies of interaction between P. parasitica-indigenous AMF from orange agroecosystems. In greenhouse also, a split root experiment with Rangpur lime was carried out. It was not possible to evaluate the indigenous AMF capacity to induce resistance because no root rot developed in Rangpur lime plants after inoculation with P. parasitica. We discuss the interaction between root pathogens in natural soil and indigenous AMF because natural soil from conventional e organic farming promoted different local and systemic root growth responses in mycorrhizal plants. Chitinase activity was similar in roots of mycorrhizal and non-mycorrhizal plants grown in conventional and organic farming soils. However, mycorhizal association increased local protein content in roots.

ASSUNTO(S)

fungo micorrízico citrus podridão-da-raiz lemon chitinase organic farming limão mycorrhizel fungus rot vaot gomose mycorrhiza agricultura orgânica fruta cítrica micorriza quitinase

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