Outbreak of Crown and Root Rot of Walnut Caused by <i>Phytophthora cinnamomi</i> in Chile

Guajardo, Jeannette; Saa, Sebastián; Camps, Rocío; Besoaín, Ximena

doi:10.1094/pdis-09-16-1242-pdn

Cited by 10 publications

(11 citation statements)

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“…Extensive dieback and mortality of N. dombeyi stands in Patagonia, Argentina was considered to be induced by droughts (Suarez, Ghermandi, & Kitzberger, 2004 to infections by P. cinnamomi eventually leading to little leaf disease and mortality (Newhook, 1959), the findings of P. cinnamomi in Valdivian rainforests could pose an additional threat to the P. radiata plantations which are already suffering from extensive needle infections and defoliations caused by the introduced airborne pathogen P. pinifolia (Durán et al, 2008;Jung et al, 2018). Prior to this study, P. cinnamomi has never been found associated with decline and die- & Besoain, 2017;Rojic & Cancino, 1975).…”

Section: Discussionmentioning

confidence: 87%

“…Prior to this study, P. cinnamomi has never been found associated with decline and dieback of natural forests in South America. The only serious diseases of trees caused by this pathogen in South America were root and crown rot of Juglans regia in horticultural plantations in central Chile and root rot and mortality of planted A. angustifolia in the Atlantic rainforests in Brazil (Dos Santos et al., ; Guajardo, Saa, Camps, & Besoain, ; Rojic & Cancino, ).…”

Section: Discussionmentioning

confidence: 99%

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Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms

Jung

Durán²,

Sanfuentes

et al. 2018

Forest Pathology

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The Valdivian rainforest, one of the global hotspots of biodiversity, is a temperate rainforest originating as a Tertiary relic from the supercontinent Gondwana. In November 2014, a survey of Phytophthora diversity was performed in 13 natural forest stands and 20 forest streams and rivers in two protected areas near Valdivia and in a temperate montane forest in the Concepción area. One planted stand each of the introduced tree species Castanea sativa and Fagus sylvatica were also included. Using baiting assays, eight described species and four previously unknown taxa of Phytophthora were isolated from 86% of the 50 rhizosphere soil samples from seven of the eight tree species sampled in 12 forest stands, and from 20 streams: P. chlamydospora, P. cinnamomi, P. kernoviae, P. lacustris, P. plurivora, P. pseudosyringae, P. ×cambivora, P. ×stagnum, P. valdiviana nom. prov. from Clade 2b, P. madida nom. prov. from Clade 8a, and P. chilensis nom. prov. and P. pseudokernoviae nom. prov. The latter two species are the closest relatives of P. kernoviae from Clade 10. Phytophthora pseudokernoviae nom. prov. was also isolated from necrotic leaves of Drimys winteri. From the Valdivia river, a swarm of three Clade 6 hybrids was recovered. Each hybrid isolate resulted from multiple reticulation events with P. thermophila as maternal and both P. amnicola and P. chlamydospora as paternal parents. In addition, three previously unknown and recently described Nothophytophthora species, N. caduca, N. chlamydospora and N. valdiviana, were isolated from several forest streams. Phytophthora cinnamomi, the most common and widespread species in soils of native forests, was associated with severe dieback of Valdivian rainforest trees, in particular D. winteri, Luma apiculata, Nothofagus dombeyi and the endangered Saxegothaea conspicua. A first pathogenicity test demonstrated high aggressiveness of P. cinnamomi to several native tree species, including N. dombeyi, Blepharocalyx cruckshanksii and Gevuina avellana.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms

Jung

Durán²,

Sanfuentes

et al. 2018

Forest Pathology

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“…This experiment served also to select the treatments (N source and dose) that were later used in the greenhouse assay described in the next section. For this experiment, the isolate PN1955 [i.e., P. cinnamomi isolated from a walnut orchard and preserved in the Fungi and Oomycetes Bank of the PPL-PUCV, and previously virulence checked by Guajardo et al (2017)], was used. This in vitro assay used a fully randomized design with a double factorial structure and five replicates.…”

Section: In Vitro Assaymentioning

confidence: 99%

“…The high N inputs used in walnut production (Gupta et al, 2012;Simorte et al, 2001;Weinbaum and Van Kessel, 1998) and the high susceptibility to P. cinnamomi reported in Juglans regia L. (Guajardo et al, 2017(Guajardo et al, , 2019 highlight the need to investigate this interaction further. The importance of assessing the severity of the disease is en-hanced by the worldwide presence of this pathogen.…”

mentioning

confidence: 99%

“…The importance of assessing the severity of the disease is en-hanced by the worldwide presence of this pathogen. For example, Guajardo et al (2017) reported that 93.3% of the walnut orchards in Chile show damage caused by oomycete species. There have been similar cases in France, Italy, Hungary, and Iran, in which species of Phytophthora have been recovered from infected walnut roots (Kurbetli, 2013).…”

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confidence: 99%

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Impact of Nitrogen Fertilization on Phytophthora cinnamomi Root-related Damage in Juglans regia Saplings

Morales¹,

Besoaín²,

Cuneo³

et al. 2019

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Excessive nitrogen (N) use in agriculture has been associated with increased severity of the damage caused by Phytophthora species. In this study, we investigated the impact in vitro and in vivo of N about Phytophthora cinnamomi. The preliminary in vitro assay showed the effect of different N sources on the mycelial growth of P. cinnamomi. This assay indicated that ammonium nitrate (NH4NO3) and ammonium sulfate [(NH4)2SO4] allowed for greater control of P. cinnamomi mycelia in comparison with calcium nitrate [Ca(NO3)2] and potassium nitrate (KNO3) when used with 1000 ppm N. The in vivo assay showed the severity of P. cinnamomi in 5-month-old Juglans regia saplings grown under greenhouse conditions. We selected NH4NH3 as the source for N for the greenhouse assay, considering the inhibitory effect on the ingrowth of P. cinnamomi and the intensive use of this fertilizer in agriculture. Walnut saplings were fertilized with 0, 35, 70, 140, 210, and 1050 ppm N and were inoculated with zoospores of P. cinnamomi 45 d after the application of nitrogen treatment (DAA). They were harvested at 90 DAA. We found that a 70-ppm N fertilization reduced the development of P. cinnamomi, resulting in lower root and canopy damage indices (DIs) than the unfertilized inoculated treatments and fertilized treatments greater than 140 ppm. The results of the in vitro and in vivo assay agree that increased N concentrations were associated with reduced mycelium growth of P. cinnamomi, providing further evidence that N fertilization can mitigate this disease. Greater root and canopy damage was observed in saplings fertilized with 1050 ppm N, regardless of whether they were inoculated with P. cinnamomi, as a result of N phytotoxicity (verified through foliar analysis). In contrast, inoculated and unfertilized saplings (N0) also showed high root and canopy DIs associated either with the inoculation with P. cinnamomi or the no fertilization treatment. We postulate that 70 ppm N is the best fertilization rate for J. regia saplings because the positive effects of N on growth are maximized and the damage caused by P. cinnamomi is mitigated.

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Plant growth-promoting rhizobacteria for protecting walnut plants from root-lesion nematode (Pratylenchus vulnus)

Pineda-Escobar,

Prodan,

Castaneda-Alvarez

et al. 2023

Eur J Plant Pathol

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Outbreak of Crown and Root Rot of Walnut Caused by Phytophthora cinnamomi in Chile

Cited by 10 publications

References 1 publication

Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms

Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptoms

Impact of Nitrogen Fertilization on Phytophthora cinnamomi Root-related Damage in Juglans regia Saplings

Plant growth-promoting rhizobacteria for protecting walnut plants from root-lesion nematode (Pratylenchus vulnus)

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