Histological characterization of resistance to Meloidogyne incognita in Avena sativa

Abstract

Root-knot nematodes, especially Meloidogyne incognita, are recognized by expressive damages on important agronomic crops worldwide. White oat (Avena sativa) is an excellent alternative to sustainable management of nematodes especially when used in crop rotation with another plant species. In this context, the aim of the present work was to study the resistance of IPR Afrodite oat cultivar to M. incognita, using histopathological methods in a comparative approach with the susceptible cultivar URSFAPA Slava. Experiments were done under greenhouse conditions, with 6 replicates for each cultivar and evaluation time. Observations of fuchsinstained roots at 3, 9, 15 and 30 days after inoculation (DAI) revealed that the resistant cultivar did not suppress nematode penetration but caused a delay in the nematode development compared with the susceptible cultivar. Moreover, mature, egg-laying females were not found in the roots of the resistant cultivar. Hypersensitive reaction (HR) was observed at 18 DAI. The HR was characterized by the formation of few giant cells of reduced size on the resistant cultivar, associated with collapsed M. incognita specimens. In most specimens, light blue fluorescence indicated lignified cells, an active plant response to nematode penetration or establishment. Intercellular spaces were of dark yellow color, indicating the presence of phenols, often associated with plant defense mechanisms to nematodes and other pathogens. Our results suggest that resistance of IPR Afrodite to M. incognita is mediated by a HR response and studies are needed to clarify the nature of compounds produced by the plant involved in the resistance.

Reaction of Avena spp. to different concentration levels of Meloidogyne javanica and M. incognita inoculum

“…The higher degree of resistance of 'IPR Afrodite' to both species of nematodes agrees to the results of research already done with this cultivar by other authors (Marini et al, 2016;Riede et al, 2015). Marini et al (2016) found a reduction in the penetration of juvenile nematodes in the roots of this oat genotype, with lignified cells and intracellular spaces filled with phenols, which is an indicative of the plant defense response to nematode attack. This suggests that the chemical profile of oat genotypes is one of the determinant Table 1.…”

“…The values of the relative density of nematodes in the root system confirms the characterization of genotypes based on the RF as they show congruence between them (Shigueoka et al, 2016). The higher degree of resistance of 'IPR Afrodite' to both species of nematodes agrees to the results of research already done with this cultivar by other authors (Marini et al, 2016;Riede et al, 2015). Marini et al (2016) found a reduction in the penetration of juvenile nematodes in the roots of this oat genotype, with lignified cells and intracellular spaces filled with phenols, which is an indicative of the plant defense response to nematode attack.…”

“…Also, the mechanisms of interaction between the nematode population and the compounds produced by resistant plants to the pathogen need better characterization in case of Avena spp. (Marini et al, 2016).…”

Histopathological characterization of Coffea arabica cultivar IPR 106 resistance to Meloidogyne paranaensis

“…HR represents one of the main plant defense mechanisms, causing histological changes after nematode penetration in coffee roots, with cell death near the J2 infection point (Silva et al, 2013). HR reactions are frequently accompanied by cell death surrounding nematode penetration, during its migration or after the establishment of the giant cell (Rodrigues et al, 2000;Marini et al, 2016).…”

“…Plant resistance mechanisms to nematode infection involve pre-or post-infectional reactions (Huang, 1985;Marini et al, 2016). One of the mechanisms involved is the hypersensitive reaction (HR), which induces histological changes after nematode penetration in root tissues, such as the death of the cells close to the giant cell induced by the nematode (Anthony et al, 2005;Albuquerque et al, 2010;Silva et al, 2013;Marini et al, 2016). Several works have been published describing the relationships between coffee and root-knot nematodes, particularly to M. incognita (Albuquerque et al, 2010) and M. exigua (Rodrigues et al, 2000;Anthony et al, 2005).…”