First Report of <i>Neofusicoccum australe</i> Causing Canker Disease and Branch Dieback on <i>Arctostaphylos glauca</i> in California

Schultheis, L. D.; Oono, Ryoko; D’Antonio, Carla M.

doi:10.1094/pdis-06-18-1026-pdn

Cited by 8 publications

(12 citation statements)

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“…However, the severity of recent canopy dieback observed suggests that this species is reaching a threshold in its drought-resistance capability. Concurrent with observations of canopy dieback, visible symptoms of fungal infection were observed (Schultheis et al, 2018) including wood cankers and leaf discoloration (green to brown and gray-black), both of which progress during prolonged drought stress, suggesting that multiple driving forces contribute to manzanita dieback.…”

mentioning

confidence: 71%

“…Cultures for inoculations were made from re-isolations of field samples that were collected in January 2016 and positively identified to be N. australe (GenBank accessions MH754931 and MH777004; Schultheis et al, 2018). Inoculations took place on 3 November 2016 (Day 0 of experiment), using methods adapted from Michailides (1991) and Swiecki and Bernhardt (2003).…”

Section: Treatmentsmentioning

confidence: 99%

“…To confirm Koch's postulates, the standard criteria to determine the agent causing a disease (Manion, 1991), we reisolated fungi from stem tissue at least 2-cm above the point of inoculation (POI) in harvested plants, amplified using primer pairs ITS1F/ITS4 for the ITS and EF1-728F/986R for alpha-elongation factor-1 (EF1). They were sequenced using the protocol described by Schultheis et al (2018).…”

Section: Treatmentsmentioning

confidence: 99%

“…Molecular sequencing identified the dominant fungal pathogen found on symptomatic A. glauca in this area to be Neofusicoccum australe , a member of the well‐known pathogenic Botryosphaeriaceae ( Bot .) family (Schultheis et al, 2018). Members of this family are most commonly associated with disease in plant species experiencing severe environmental stress (Schoeneweiss, 1981; Desprez‐Loustau et al, 2006; Slippers and Wingfield, 2007), including Arctostaphylos spp.…”

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confidence: 99%

“…The present study was aimed at identifying the possible role of N. australe in A. glauca dieback in Santa Barbara County, particularly in combination with extreme drought. Because this pathogen has only recently been reported on wild shrub species in California (Schultheis et al, 2018) and is thought to be an introduced species native to Western Australia (Sakalidis et al, 2011), this outbreak represents a new and undescribed threat to these wildland plant assemblages.…”

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confidence: 99%

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Mechanisms of severe dieback and mortality in a classically drought‐tolerant shrubland species (Arctostaphylos glauca)

Drake-Schultheis

Oono

D’Antonio

2020

American J of Botany

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Premise Mortality events involving drought and pathogens in natural plant systems are on the rise due to global climate change. In Santa Barbara, California, United States, big berry manzanita (Arctostaphylos glauca) has experienced canopy dieback related to a multi‐year drought and infection from fungal pathogens in the Botryosphaeriaceae family. A greenhouse experiment was conducted using Neofusicoccum australe to test the specific influences of drought and fungal infection on A. glauca. Methods A full factorial design was used to compare four treatment groups (drought + inoculation; drought – inoculation; watering + inoculation; and control: watering – inoculation). Data were collected for 10 weeks on stress symptoms, changes in leaf fluorescence and photosynthesis, and mortality. Results Results indicated significant effects of watering and inoculation treatments on net photosynthesis, dark‐adapted fluorescence, and disease symptom severity (P < 0.05), and a strong correlation was found between physiological decline and visible stress (P < 0.0001). Mortality differed between treatments, with all groups except for the control experiencing mortality (43% mortality in drought – inoculation, 83% in watering – inoculation, and 100% in drought + inoculation). A Kaplan–Meier survival analysis showed drought + inoculation to have the least estimated survivorship compared to all other treatment groups. Conclusions In addition to a possible synergistic interaction between drought and fungal infection in disease onset and mortality rates in A. glauca, these results indicate that young, non‐drought‐stressed plants are susceptible to mortality from N. australe infection, with important implications for the future of wildland shrub communities.

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confidence: 71%

Section: Treatmentsmentioning

confidence: 99%

Section: Treatmentsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Mechanisms of severe dieback and mortality in a classically drought‐tolerant shrubland species (Arctostaphylos glauca)

Drake-Schultheis

Oono

D’Antonio

2020

American J of Botany

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Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

Pratt

2021

American J of Botany

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Woody, evergreen shrublands are the archetypal community in mediterranean‐type ecosystems, and these communities are profoundly changed when they undergo vegetation‐type conversion (VTC) to become annual, herb‐dominated communities. Recently, VTC has occurred throughout southern California chaparral shrublands, likely with changes in important ecosystem functions. The mechanisms that lead to VTC and subsequent changes to ecosystem processes are important to understand as they have regional and global implications for ecosystem services, climate change, land management, and policy. The main drivers of VTC are altered fire regimes, aridity, and anthropogenic disturbance. Some changes to ecosystem function are certain to occur with VTC, but their magnitudes are unclear, whereas other changes are unpredictable. I present two hypotheses: (1) VTC leads to warming that creates a positive feedback promoting additional VTC, and (2) altered nitrogen dynamics create negative feedbacks and promote an alternative stable state in which communities are dominated by herbs. The patterns described for California are mostly relevant to the other mediterranean‐type shrublands of the globe, which are biodiversity hotspots and threatened by VTC. This review examines the extent and causes of VTC, ecosystem effects, and future research priorities.

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Determining potential drivers of vegetation change in a Mediterranean environment

2022

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The increased occurrences of drought and fire may be contributing to the loss of biodiverse ecosystems in Mediterranean regions. Specifically, the conversion of diverse native shrublands, such as chaparral, to non-native annual grassland by fire is of great conservation concern in California. To avoid or slow the loss of chaparral, it is important to understand the underlying causes of landscape conversion. Studies investigating the interaction of multiple potential drivers are particularly crucial to identification of vulnerable areas of the landscape.Here we used aerial imagery to evaluate vegetation transitions between chaparral, sage scrub, grassland, and tree domination and their potential drivers within Ventura County, CA, a strongly Mediterranean climate region. We used random forest algorithms and conditional inference trees to determine the climatic, topographic, and fire-related variables contributing most to vegetation change. Our results support that chaparral conversion to grass (27% of chaparral plots) is a result of landscape position, fire, and drought acting in tandem. In particular, lower elevation, southwest-facing slopes that experience a postfire drought are at very high likelihood of conversion to non-native annual grass. Additionally, our results show that these grasslands, once formed, rarely convert to other community types. Therefore, protecting shrub-dominated areas that are most likely to convert (low elevation, more southwest-facing slopes, and less annual precipitation) is crucial to preserving native vegetation diversity.

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First Report of Neofusicoccum australe Causing Canker Disease and Branch Dieback on Arctostaphylos glauca in California

Cited by 8 publications

References 5 publications

Mechanisms of severe dieback and mortality in a classically drought‐tolerant shrubland species (Arctostaphylos glauca)

Mechanisms of severe dieback and mortality in a classically drought‐tolerant shrubland species (Arctostaphylos glauca)

Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

Determining potential drivers of vegetation change in a Mediterranean environment

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