Abstract
Since 2001 widespread mortality of black walnut (Juglans nigra) has been reported in Colorado, USA. Affected trees initially show a yellowing and thinning of leaves in the upper crown, followed by twig and branch dieback and ultimately tree death. We report that this mortality is the result of a combination of an expanded geographic range of the walnut twig beetle (Pityophthorus juglandis), its aggressive feeding behavior on black walnut, and extensive cankering caused by a filamentous ascomycete in the genus Geosmithia (Ascomycota: Hypocreales). Thirty seven Geosmithia strains collected from J. californica, J. hindsii, J. major, and J. nigra in eight USA states (AZ, CA, CO, ID, OR, UT, WA) were compared using morphological and molecular methods (ITS rDNA sequences). Strains had common characteristics including a yellowish color of conidia en masse, growth at 37°C, and absence of growth on Czapek-Dox agar and belonged to a single species described here as G. morbida. G. morbida is the first Geosmithia species documented as a plant pathogen. We also tested the susceptibility of hickory and walnut species to G. morbida in greenhouse and field studies. Carya illinoinensis, C. aquatica, and C. ovata were immune. All walnut species tested, including J. ailantifolia, J. californica, J. cinerea, J. hindsii, J. major, J. mandshurica, J. microcarpa, J. nigra and J. regia developed cankers following inoculation with G. morbida. J. nigra had the largest cankers, whereas J. major, a native host of the WTB and presumably G. morbida, had smaller and more superficial cankers. Canker size differed among maternal half-sibling families of J. nigra and J. cinerea, indicating genetic variability in resistance to G. morbida. Our inoculation studies with G. morbida have corroborated many of the field observations on susceptibility of hickory and walnut species to TCD, although the ability of the WTB to successfully attack and breed in walnuts is also an important component in TCD resistance.
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Claims 9
Claim · model-written summary
Black walnut mortality results from an expanded range of the walnut twig beetle, its aggressive feeding, and cankering by Geosmithia.
- Taxon
- black walnut
Juglans nigrae1 - Interactor
- GeosmithiaGeosmithiae1pathogen
- Second interactor
- Pityophthorus juglandisPityophthorus juglandise1pest
- Outcome
- mortalitye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“this mortality is the result of a combination of an expanded geographic range of the walnut twig beetle (Pityophthorus juglandis), its aggressive feeding behavior on black walnut, and extensive cankering caused by a filamentous ascomycete in the genus Geosmithia”
Claim · model-written summary
Thirty-seven Geosmithia strains from four Juglans species in eight USA states belonged to a single species, G. morbida.
- Taxon
- J. californica, J. hindsii, J. major, and J. nigraJuglans nigra
Juglans californica
Juglans hindsii
Juglans majore1 - Interactor
- G. morbidaGeosmithia morbidae2pathogen
- Outcome
- single speciese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Thirty seven Geosmithia strains collected from J. californica, J. hindsii, J. major, and J. nigra”
e2“Strains had common characteristics including a yellowish color of conidia en masse, growth at 37°C, and absence of growth on Czapek-Dox agar and belonged to a single species described here as G. morbida”
Claim · model-written summary
G. morbida is the first Geosmithia species documented as a plant pathogen of walnut.
- Taxon
- walnutt0
- Interactor
- G. morbidaGeosmithia morbidae4pathogen
- Outcome
- documented as a plant pathogene4
Verbatim
t0“susceptibility of walnut and hickory species to thousand cankers disease”
e4“G. morbida is the first Geosmithia species documented as a plant pathogen”
Claim · model-written summary
Carya illinoinensis, C. aquatica and C. ovata were immune to G. morbida.
- Taxon
- Carya illinoinensis, C. aquatica, and C. ovata
_1_(24790682337).jpg?width=60)
Carya illinoinensis_(27074521002).jpg?width=60)
Carya ovata
Carya aquaticae5 - Interactor
- G. morbidaGeosmithia morbidae6pathogen
- Outcome
- immunee5
- Setting
- greenhouse and field studiese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_1_(24790682337).jpg?width=500)
_(27074521002).jpg?width=500)
Verbatim
e5“Carya illinoinensis, C. aquatica, and C. ovata were immune”
e6“We also tested the susceptibility of hickory and walnut species to G. morbida in greenhouse and field studies”
Claim · model-written summary
All walnut species tested developed cankers following inoculation with G. morbida.
- Taxon
- walnut speciese7
- Treatment
- inoculation with G. morbidae7
- Interactor
- G. morbidaGeosmithia morbidae7pathogen
- Outcome
- cankerse7
Not reportedComparatorDirection
Verbatim
e7“All walnut species tested, including J. ailantifolia, J. californica, J. cinerea, J. hindsii, J. major, J. mandshurica, J. microcarpa, J. nigra and J. regia developed cankers following inoculation with G. morbida”
Claim · model-written summary
Juglans nigra had the largest cankers among the tested walnuts, larger than J. major.
- Taxon
- J. nigraJuglans nigrae0
- Interactor
- G. morbidaGeosmithia morbidae0pathogen
- Outcome
- cankerse0
- Direction
- largeste0
- Comparator
- J. majore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“J. nigra had the largest cankers, whereas J. major, a native host of the WTB and presumably G. morbida, had smaller and more superficial cankers”
Claim · model-written summary
Juglans major had smaller and more superficial cankers than J. nigra.
- Taxon
- J. majorJuglans majore0
- Interactor
- G. morbidaGeosmithia morbidae0pathogen
- Outcome
- cankerse0
- Direction
- smallere0
- Qualifier
- more superficiale0
- Comparator
- J. nigrae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“J. nigra had the largest cankers, whereas J. major, a native host of the WTB and presumably G. morbida, had smaller and more superficial cankers”
Claim · model-written summary
Canker size differed among maternal half-sibling families of J. nigra and J. cinerea, indicating genetic variability in resistance to G. morbida.
- Taxon
- J. nigra and J. cinereaJuglans nigra
Juglans cinereae0 - Material
- maternal half-sibling familiese0
- Interactor
- G. morbidaGeosmithia morbidae0pathogen
- Outcome
- Canker sizee0
- Qualifier
- genetic variability in resistance to G. morbidae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Canker size differed among maternal half-sibling families of J. nigra and J. cinerea, indicating genetic variability in resistance to G. morbida”
Claim · model-written summary
The ability of the walnut twig beetle to attack and breed in walnuts is an important component of thousand cankers disease resistance.
- Interactor
- WTBe0pest
- Outcome
- TCD resistancee0
- Qualifier
- ability of the WTB to successfully attack and breed in walnutse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the ability of the WTB to successfully attack and breed in walnuts is also an important component in TCD resistance”