Interações entre acessos de fáfia [Pfaffia glomerata (Spreng.) Pedersen] com nematoides (Meloidogyne incognita e M. javanica): aspectos fitoquímicos e estruturais

• Autor(a) principal: Cruz, Ana Claudia Ferreira da
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/372
• topic: Pfaffia glomerata; Interação; Nematoide; Pfaffia glomerata; interaction; nematode; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Species of the genus Pfaffia, belonging to the family Amaranthaceae, contains significant levels of ecdysteroids. In Pfaffia glomerata (Spreng.) Pedersen, the determination of β-ecdysone (20E), ecdysteroid of interest, has been carried out mainly in the roots. Brazil is currently the largest producer and exporter of this species, but there are limiting factors that affect plant growth and crop production. Nematodes of the genus Meloidogyne are among the main diseases of the root system, causing galls and rot of the root system. However, the presence of these nematodes has increased the amount of 20E in different accessions of Pfaffia, which is correlated to the possible positive interaction between nematode development and production of the active ingredient in the plant, since 20E is similar to the hormones involved in ecdysis. Thus, this study evaluated two accessions of P. glomerata [2202-15 (AC 22) and 2209-09 (AC 43)] propagated in vitro and at 30 days of cultivation after acclimatization, in interaction with Meloidogyne. The split-root system technique was used to avoid the toxic effects of the inducing agent (nematode) on the host plants (Pfaffia), with concentrations of 0, 6000, 12000, 18000, 24000 and 30000 M. Incognita eggs inoculated into the containers, characterizing the treatments with and without nematode eggs. The study evaluated the systemic communication between roots, the accumulation of the active ingredient (20E) and determined the tolerance of both accessions to the nematode M. incognita and the activity of enzymes indicative of the induction of plant resistance. Phytochemical, anatomical and histochemical aspects of the interaction of the accesses AC 22 and AC 43 infected by Meloidogyne incognita and M. Javanica were also analyzed. For this purpose, three plant combinations were grown in the same container (22/22, 43/43 or 22/43). Interference was observed, such as competition between Pfaffia accesses, in which the presence of nematode influenced 20E production. This competition led to less tolerance of the accesses to the nematodes M. incognita and M. javanica. Anatomical analysis showed that Meloidogyne infected root vascular cylinders, particularly in AC 22, had a high number of giant, multinucleated, densely cytoplasmic cells, and compression of cortical cells and vascular cylinder 10 caused by the feeding sites. These sites compressed the xylem elements in the two accessions, although AC 43 had less giant cells along the root system compared with AC 22. These data were also confirmed by the analysis of number of galls and eggs. The histochemical tests showed positive reaction of plants attacked by the nematodes, whereas the control plants showed less intense staining with the dyes PAS, Sudan and xylidine Ponceau. The production of enzymes indicative of the induction of plant resistance, in combination with the accesses and nematode eggs inoculated into each container, showed that there was partial deactivation of the control of the oxidative pathway, as well as of the constitutive synthesis of phenolic compounds and chitinases.