Characterization of Lilium longiflorum cv. ‘Nellie White’ Infection with Root-lesion Nematode Pratylenchus penetrans by Bright-field and Transmission Electron Microscopy

Abstract

Lilium longiflorum cv. Nellie White, commonly known as Easter lily, is an important floral crop with an annual wholesale value of over $26 million in the United States. The root-lesion nematode, Pratylenchus penetrans, is a major pest of lily due to the significant root damage it causes. In this study, we investigated the cytological aspects of this plant-nematode interaction using bright-field and transmission electron microscopy. We took advantage of an in vitro culture method to multiply lilies and follow the nematode infection over time. Phenotypic reactions of roots inoculated with P. penetrans were evaluated from 0 to 60 d after nematode infection. Symptom development progressed from initial randomly distributed discrete necrotic areas to advanced necrosis along entire roots of each inoculated plant. A major feature characterizing this susceptible host response to nematode infection was the formation of necrosis, browning, and tissue death involving both root epidermis and cortical cells. Degradation of consecutive cell walls resulted in loss of cell pressure, lack of cytoplasmic integrity, followed by cell death along the intracellular path of the nematode's migration. Pratylenchus penetrans was never seen in the vascular cylinder as the layer of collapsed endodermal cells presumably blocked the progression of nematodes into this area of the roots. This study presents the first detailed cytological characterization of P. penetrans infection of Easter lily plants.

Identification of candidate effector genes of Pratylenchus penetrans

“…Using the current datasets of P. penetrans , both of these phenomena appear to be specific features to these effectors. It is well documented that infection by RLNs induces the production and accumulation of tannin‐like deposits (Townshend et al ., ; Vieira et al ., ). Tannins are astringent polyphenols induced on wounding and may contribute to the induced defence response (War et al ., ).…”

Cellular and Transcriptional Responses of Resistant and Susceptible Cultivars of Alfalfa to the Root Lesion Nematode, Pratylenchus penetrans

“…Nematodes were re-cultured every 2 months onto new ex-roots of corn and maintained in the dark at 25°C. Nematodes were prepared and plant inoculation performed as described by Vieira et al (2017). Briefly, nematodes were extracted by placing infected roots on a wire sieve in a sterilized glass bowl filled with distilled water containing 50 mg/L carbenicillin and 50 mg/L kanamycin.…”

Assessment of the pest status of Pratylenchus curvicauda and ultrastructural changes in roots of infected wheat and barley

“…The behaviour of P. curvicauda and the destructive cellular changes induced in the susceptible wheat and barley cultivars were similar to those of many Pratylenchus spp. (Acosta and Malek, 1981;Townshend et al, 1989;Zunke, 1990aZunke, , 1990bVieira et al, 2017). The presence, distribution, and appearance of the nematodes in host cells were similar in both wheat and barley plants.…”

“…Also, limiting the nematode to cortical tissues may protect the host plants from more severe damage and enable water and nutrients to continue to be transported to the aerial plant tissues. Tannin-like depositions in the nematode-infected root cells, which is usually associated with cytoplasmic disorganization and lack of membrane integrity, has been reported after the infection of different plants by P. penetrans (Townshend et al, 1989;Vieira et al, 2017Vieira et al, , 2019. Also, the thickened cell walls could reflect the deposition of condensed and granular cytoplasm against the walls.…”

“…Also, the thickened cell walls could reflect the deposition of condensed and granular cytoplasm against the walls. These depositions are often observed as a defence response by plants against pathogen attack and have been suggested as a mechanism by which host plants resist disease progression (Vieira et al, 2017). Accumulation of more tannin-like deposits in cells of resistant cultivars of alfalfa following an infection of P. penetrans has led to the suggestion that the reaction is a resistance mechanism against the root-lesion nematode (Vieira et al, 2019).…”