Location: Floral and Nursery Plants ResearchTitle: Symptom development in response to combined infection of in vitro grown Lilium longiflorum with the root lesion nematode Pratylenchus penetrans and soilborne fungi collected from diseased roots of field-grown lilies
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2017
Publication Date: 2/14/2017
Citation: Vieira, P., Lakshman, D.K., Pandey, R., Slovin, J.P., Kamo, K.K. 2017. Symptom development in response to combined infection of in vitro grown Lilium longiflorum with the root lesion nematode Pratylenchus penetrans and soilborne fungi collected from diseased roots of field-grown lilies. Plant Disease. 101:1-8.
Interpretive Summary: Easter lilies are grown primarily in the Pacific Northwest for bulb production, and are susceptible to attack by Pratylenchus penetrans, the root lesion nematode. In order to study how the infection by thte nematode is affected by the presence of fungal pathogens, we isolated ten different fungal samples from diseased roots of Easter lilies, including Fusarium oxysporum, Fusarium tricinctum, and Rhizoctonia AG-I. This is the first report of Rhizoctonia AG-I infecting lilies worldwide and the first report of Fusarium tricinctum infecting lilies in the U.S. These fungal isolates were shown to cause necrosis and root-rot of lily roots in culture. Disease symptoms appeared faster when the lilies had been inoculated with root lesion nematodes prior to inoculating with each of the fungal isolates. This study characterizes a complex set of soil pathogens that cause disease in Easter lily, and will be useful in developing effective treatment and control of diseases in this important crop.
Technical Abstract: Eight fungal isolates (ELRF 1-8) were isolated from necrotic roots of Lilium longiflorum cv. Nellie White (Easter lily) grown in a field in the U.S. Pacific Northwest. The eight fungal isolates were identified by sequencing and molecular phylogenetic analyses based on their ITS rDNA region. Five isolates were identified as Fusarium oxysporum, two as Fusarium tricinctum, and one as Rhizoctonia sp. AG-I. This constitutes the first report of Rhizoctonia sp. AG-I infecting lilies and the first report of Fusarium tricinctum infecting lilies in the U.S. To study and validate their pathogenicity, pure cultures of each isolate were used to infect the roots of Easter lily plants growing in vitro. In addition, some Easter lily plants growing in vitro were infected with Pratylenchus penetrans, the root lesion nematode, prior to placing a culture plug of fungus 1 cm from a lily root. P. penetrans is a nematode species commonly found in the sampled fields. The presence of both Rhizoctonia sp. AG-I isolate ELRF 3 and nematodes in infected lilies was evaluated by molecular analyses confirming the infection of roots three days after inoculation, even though disease symptoms were not observed at that time. Necrosis and root rot symptoms developed faster with all eight fungal isolates when there had been prior infection with P. penetrans, the major nematode parasitizing Easter lily roots in the field in Oregon.