Impact of Laurel Wilt, Caused by<i>Raffaelea lauricola</i>, on Leaf Gas Exchange and Xylem Sap Flow in Avocado,<i>Persea americana</i>

Ploetz, R. C.; Schaffer, Bruce; Vargas, Ana I.; Konkol, Joshua L.; Salvatierra, Juanpablo; Wideman, Ronney

doi:10.1094/phyto-07-14-0196-r

Cited by 27 publications

(23 citation statements)

References 34 publications

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“…In dual‐culture assays on potato dextrose agar (PDA), 32 fungi (24 OTUs) that were most prevalent in prior assays of avocado xylem (J. Pérez‐Martínez, unpublished data) were evaluated against CBS 127349, a virulent isolate of R. lauricola used in previous laurel wilt studies (Ploetz et al ., , ; Table ). Mycelial plugs, 0.5 cm in diameter, of the pathogen and a given endophyte were placed 5 cm from each other in 9‐cm‐diameter Petri plates containing PDA and were incubated on a laboratory bench at 25 °C under ambient light conditions.…”

Section: Methodsmentioning

confidence: 96%

“…Endophyte colonization and protection of trees from subsequent inoculation with CBS 127349 was examined in three greenhouse experiments with avocado cultivars that were susceptible to laurel wilt (Ploetz et al ., , ; Table ). For each experiment, trees (clonal scions grafted on seedling rootstocks) in 11.35 L pots were obtained from a local commercial nursery; plants were c .…”

Section: Methodsmentioning

confidence: 96%

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Significant in vitro antagonism of the laurel wilt pathogen by endophytic fungi from the xylem of avocado does not predict their ability to control the disease

2018

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The ascomycete Raffaelea lauricola causes laurel wilt, a lethal vascular disease of avocado, Persea americana, and other members of the Lauraceae plant family. Few effective control measures for laurel wilt exist and new measures are needed. In this study, biological control of the disease with endophytic fungi from avocado was examined. Thirty-two endophytes (24 operational taxonomic units or OTUs) isolated from the xylem of healthy trees (the infection court of R. lauricola) were evaluated against R. lauricola with in vitro dual-culture assays. Nine OTUs that showed strong in vitro antagonism of the pathogen were tested in planta against laurel wilt. In three greenhouse experiments, grafted avocado plants of Simmonds or Russell cultivars, which are both susceptible to laurel wilt, were inoculated with endophytes and, after 10-16 days, inoculated with the same isolate of R. lauricola that was used in the in vitro assays. Within 14 days of inoculation with R. lauricola, laurel wilt developed in plants that were not treated with endophytes (positive controls) but also developed in endophyte-treated plants to the extent observed in the positive controls (P = 0.05). The pathogen colonized plants rapidly and systemically, but endophytes generally did not colonize xylem more than 2 cm above the point at which plants were inoculated. Although the tested endophytes strongly antagonized the pathogen in vitro, this did not translate to an ability to reduce development of laurel wilt. The management of laurel wilt and other plant diseases with fungal endophytes is discussed.

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Section: Methodsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 96%

Significant in vitro antagonism of the laurel wilt pathogen by endophytic fungi from the xylem of avocado does not predict their ability to control the disease

2018

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“…Hybridization occurs freely among the races and is associated with a range of responses to calcareous soil, salinity, high and low temperatures, and other stresses [109,116]. Different responses to laurel wilt have also been noted among the races and racial combinations of the species; in general, greater susceptibility occurs in WI cultivars [117,118].…”

Section: Hosts Of Laurel Wiltmentioning

confidence: 99%

“…[121] observed that less than 1% of the lumena of avocado, swamp bay and camphortree were colonized with a GFP-labelled strain of Raffaelea lauricola, even 30 days after inoculation (dai) (when most plants of avocado and swamp bay had died from laurel wilt). Ploetz et al [118] hypothesized that an avocado scion's susceptibility to laurel wilt is related to its ability to conduct water. They observed that pre-inoculation sap flow rates were greater (p = 0.05) in a susceptible cultivar, "Russell" WI, compared to the less susceptible cultivars "Brogdon" M × G × WI and "Marcus Pumpkin" G; however, sap flow plummeted in "Russell" soon after inoculation.…”

Section: Host Responses To Infection By Raffaelea Lauricolamentioning

confidence: 99%

“…As the disease develops, host trees increase the production of volatiles that attract X. glabratus [92], which then promotes mass attack, colonization and brood development by X. glabratus. Ploetz et al [118] hypothesized that an avocado scion's susceptibility to laurel wilt is related to its ability to conduct water. They observed that pre-inoculation sap flow rates were greater (p = 0.05) in a susceptible cultivar, "Russell" WI, compared to the less susceptible cultivars "Brogdon" M × G × WI and "Marcus Pumpkin" G; however, sap flow plummeted in "Russell" soon after inoculation.…”

Section: Ecology and Epidemiologymentioning

confidence: 99%

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Laurel Wilt in Natural and Agricultural Ecosystems: Understanding the Drivers and Scales of Complex Pathosystems

Ploetz

Kendra²,

Choudhury

et al. 2017

Forests

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Laurel wilt kills members of the Lauraceae plant family in the southeastern United States. It is caused by Raffaelea lauricola T.C. Harr., Fraedrich and Aghayeva, a nutritional fungal symbiont of an invasive Asian ambrosia beetle, Xyleborus glabratus Eichhoff, which was detected in Port Wentworth, Georgia, in 2002. The beetle is the primary vector of R. lauricola in forests along the southeastern coastal plain of the United States, but other ambrosia beetle species that obtained the pathogen after the initial introduction may play a role in the avocado (Persea americana Miller) pathosystem. Susceptible taxa are naïve (new-encounter) hosts that originated outside Asia. In the southeastern United States, over 300 million trees of redbay (P. borbonia (L.) Spreng.) have been lost, and other North American endemics, non-Asian ornamentals and avocado-an important crop that originated in MesoAmerica-are also affected. However, there are no reports of laurel wilt on the significant number of lauraceous endemics that occur in the Asian homeland of R. lauricola and X. glabratus; coevolved resistance to the disease in the region has been hypothesized. The rapid spread of laurel wilt in the United States is due to an efficient vector, X. glabratus, and the movement of wood infested with the insect and pathogen. These factors, the absence of fully resistant genotypes, and the paucity of effective control measures severely constrain the disease's management in forest ecosystems and avocado production areas.

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Identification of the Achilles heels of the laurel wilt pathogen and its beetle vector

Zhou

Avery

Carrillo

et al. 2018

Appl Microbiol Biotechnol

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Ambrosia beetles harbor fungal symbionts that serve as food sources for larvae and adults. These beetles lay their eggs along tunnels in xylem sapwood, which is the substrate for fungal growth. Symbiotic fungi of the genus Raffaelea found in invasive and indigenous ambrosia beetles include the highly virulent plant pathogen Raffaelea lauricola affecting members of the Lauraceae family. R. lauricola is responsible for the deaths of > 500 million trees since 2005. Infection by as few as 100 spores can kill a healthy tree within months. Our data show that R. lauricola is cold-adapted with optimal growth between 16 and 26 °C, with little to no growth at temperatures ≥ 30 °C. The fungus is halophilic and shows a dramatic decrease in growth at pH ≥ 6.8. Fungicide resistance profiling revealed sensitivity of R. lauricola to prochloraz, dichlorofluanid, most conazoles, dithiocarbamates, and zineb (zinc fungicide), whereas the related species Raffaelea arxii showed more limited fungicide sensitivity. Entomopathogenic fungi potentially useful for beetle control were generally highly resistant to most fungicides tested. Coupling pH decreased the concentration for 95% inhibition of fungal growth (IC) of the most potent R. lauricola fungicides by 3-4-fold. Use of avocado bark plug insect bioassays revealed that commercially available Beauveria bassiana can be used as a biological control agent capable of effectively killing the beetle vectors. These data provide simple and practical recommendations to specifically target R. lauricola while having minimal effects on other symbiotic and entomopathogenic fungi, the latter of which can be used to manage the beetle vectors.

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Impact of Laurel Wilt, Caused byRaffaelea lauricola, on Leaf Gas Exchange and Xylem Sap Flow in Avocado,Persea americana

Cited by 27 publications

References 34 publications

Significant in vitro antagonism of the laurel wilt pathogen by endophytic fungi from the xylem of avocado does not predict their ability to control the disease

Significant in vitro antagonism of the laurel wilt pathogen by endophytic fungi from the xylem of avocado does not predict their ability to control the disease

Laurel Wilt in Natural and Agricultural Ecosystems: Understanding the Drivers and Scales of Complex Pathosystems

Identification of the Achilles heels of the laurel wilt pathogen and its beetle vector

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