Restoration outplantings of nursery-origin
Californian flora are heavily infested with
Phytophthora
Tyler B Bourret, HK Mehl, DM Rizzo, TJ Swiecki,
EA Bernhardt & JM Hillman 6th SOD Symposium, June 23, 2016
Survey of potentially infested restoration sites
Santa Clara Valley Water District (SCVWD) has routinely performed restoration with nursery-reared native Californian flora
Phytophthora species had been previously isolated from SCVWD outplantings & associated nurseries by Phytosphere (TJ Swiecki & EA Bernhardt), including P. tentaculata #5 on APHIS list of species to keep out of US
Broad survey of 31 sites by Rizzo lab (H. Mehl & T. Bourret) & Phytosphere Sep 2015 - May 2016
31 restoration sites sampled
San Jose
Sample site
36 plant species 193 samples collected Preference for symptomatic plants, especially known P. tentaculata hosts ~1 L soil + roots
Methods - soil sample processing & ID
Baited with green pears & Rhododendron leaves
Strains determined to species using morphotyping & ITS sequences
Pythium s.l. was included but not reported (Mostly Phytopythium & Pythium s.s.)
► Phytophthora recovered
Plant species Common name # samples # positive samples % samples
# Positive sites # Psp.
► Aesculus californica Buckeye 2 1 50 1 1
► Acer negundo Boxelder maple 5 3 60 2 2
► Alnus rhombifolia White Alder 2 1 50 1 1
► Artemisia californica California sagebrush 8 2 25 1 3
► Artemisia douglasiana Mugwort 23 6 26 3 16 Aster chilensis Chilean aster 3 0 0 0 0
► Baccharis glutinosa Salt marsh baccharis 1 1 100 1 2 Baccharis pilularis Coyote brush 3 0 0 0 0
► Baccharis salicifolia Mulefat 3 1 33 1 4
► Ceanothus thyrsiflorus Blue blossom 1 1 100 1 3 Clematis ligusticifolia Virgin's bower 2 0 0 0 0
► Dead plant (unknown sp.) Empty planting site 8 2 25 2 2
► Diplacus aurantiacus Sticky monkey flower 7 5 71 2 6
► Euthamia occidentalis Goldenrod 3 2 67 2 1
► Frangula californica Coffeeberry 9 2 22 2 2 Helenium bignonia Sneezeweed 1 0 0 0 0
► Heteromeles arbutifolia Toyon 18 12 67 9 5
► Juncus sp. Rush (unknown sp.) 6 5 83 4 7 Lepechinia calycina Pitcher sage 1 0 0 0 0
► Platanus racemosa Sycamore 7 1 14 1 2
► Populus fremontii Fremont cottonwood 4 2 50 1 3
► Prunus ilicifolia Holly-leaf cherry 2 1 50 1 1
► Quercus agrifolia Coast live oak 19 5 26 3 5
► Quercus douglasiana Blue oak 3 1 33 1 2
► Quercus lobata Valley oak 12 4 33 1 3 Quercus sp. Oak (unknown sp.) 1 0 0 0 0
► Quercus wislizenii Canyon live oak 1 1 100 1 1 Rhamnus crocea Redberry buckthorn 2 0 0 0 0
► Rosa californica CA wild rose 13 7 54 4 6
► Rubus ursinus CA blackberry 3 1 33 1 1
► Salicornia pacifica Pickleweed 3 2 67 1 2
► Salix sp. Willow (unknown sp.) 1 1 100 1 6
► Sambucus mexicana Blue elderberry 12 4 33 4 4 Sambucus racemosa Mexican elderberry 2 0 0 0 0
► Sambucus sp. Elderberry (unknown sp.) 1 1 100 1 2
► Symphoricarpos laevigatus Snowberry 4 1 25 1 1
► Umbellularia californica Bay laurel 1 1 100 1 2
193 total samples 74 Phytophthora- positive 27 yielded more than one species 36 plant species (28 associated with positive samples)
Plant species Common name # samples # positive samples # Psp. Phytophthora species list
Artemisia douglasiana Mugwort 23 6 16 CAS, CHL, CRA, CRY, HYD, INU, LAC, MUL, PAR, PIN, POLxMAR, ROS, MUG, OAK, THE, THExAMN
Juncus sp. Rush (unknown sp.) 6 5 7 CAC, CRY, EUR, INU, JUN, MUL, PIN
Diplacus aurantiacus Sticky monkey flower 7 5 6 CAC, CRA, EUR, INU, MEG, PIN
Rosa californica CA wild rose 12 6 6 CAC, CRA, MEG, QUM, RAM. RIP
Salix sp. Willow (unknown sp.) 1 1 6 CRA, CRY, LAC, PSE, ROS, OAK
Quercus agrifolia Coast live oak 19 5 5 CAC, CRA, OAK, SYR, WAL
Heteromeles arbutifolia Toyon 18 12 5 CAC*, CRA, CRY, HED, OAK
Baccharis salicifolia Mulefat 3 1 4 ASP, KELxCRY, ROS, OAK
Sambucus mexicana Mexican elderberry 12 4 4 CRA, PAL, QUE, RAS
Populus fremontii Fremont cottonwood 4 2 3 ACE, PSE, ROS
Ceanothus thyrsiflorus Blue blossom 1 1 3 CAC, MUL, NIC
Quercus lobata Valley oak 12 4 3 CAC, QUE, PSY
Artemisia californica California sagebrush 8 2 3 CRA, INU, PAL
Acer negundo Boxelder maple 5 3 2 CAC, MUL
Frangula californica Coffeeberry 9 2 2 CAC, MUL
Quercus douglasiana Blue oak 3 1 2 CAC, OCC
Dead plant (unknown sp.) Empty planting site 8 1 2 CAC, ROS
Salicornia pacifica Pickleweed 3 2 2 HUM, HUMxINU
Baccharis glutinosa Salt marsh baccharis 1 1 2 MUL, OAK
Umbellularia californica Bay laurel 1 1 2 MUL, OCC
Sambucus sp. Elderberry 1 1 2 MUL, ROS
Platanus racemosa Sycamore 7 1 2 ROS, OAK
Aesculus californica Buckeye 2 1 1 CAC
Alnus rhombifolia White Alder 2 1 1 CAC
Euthamia occidentalis Goldenrod 3 2 1 CAC
Prunus ilicifolia Holly-leaf cherry 2 1 1 CAC
Rubus ursinus CA blackberry 3 1 1 CAC
Symphoricarpos laevigatus Snowberry 4 1 1 CAC
Quercus wislizenii Canyon live oak 1 1 1 PIN
Aster chilensis Chilean aster 3 0 0
Baccharis pilularis Coyote brush 3 0 0
Clematis ligusticifolia Virgin's bower 2 0 0
Helenium bignonia Sneezeweed 1 0 0
Lepechinia calycina Pitcher sage 1 0 0
Quercus sp. Oak (unknown sp.) 1 0 0
Rhamnus crocea Redberry buckthorn 2 0 0
Sambucus racemosa Red elderberry 2 0 0
Many species from preferentially sampled hosts: - Mugwort - Toyon - Monkey flower - Oak spp.
Also many species from: - Willow - Juncus sp. - Mulefat
P. acerina, ACE; P. asparagi, ASP; P. cactorum, CAC, P. chlamydospora, CHL; P. crassamura, CRA; P. europaea, EUR; P. hedraiandra, HED; P. hydropathica, HYD; P. humicola, HUM; P. humicola x inundata, HUMxINU; P. inundata, INU; P. sp. kelmania, KEL; P. lacustris, LAC; P. megasperma species complex, MEG; P. multivora, MUL; P. nicotianae, NIC; P. occultans, OCC; P. palmivora, PAL; P. parsiana, PAR; P. pini, PIN; P. polonica X aff. "Maryland 8," POLxMAR; P. pseudocryptogea , PCY; P. pseudosyringae, PSE; P. psychrophila, PSY; P. quercetorum, QUM; P. quercina, QUE; P. ramorum, RAM; P. riparia, RIP; P. rosacearum, ROS; P. syringae, SYR; P. taxon casuarina, CAS; P. taxon juncus (sp. nov.), JUN; P. taxon mugwort (sp. nov.), MUG; P. taxon oaksoil, OAK; P. taxon raspberry, RAS; P. taxon walnut, WAL; P. thermophila, THE; P. thermophila
X amnicola, THExAMN *All Phytophthora positive samples included this Psp.
Phytophthora species recovered, by site
P. acerina, ACE; P. asparagi, ASP; P. cactorum, CAC, P. chlamydospora, CHL; P. crassamura, CRA; P. europaea, EUR; P. hedraiandra, HED; P. hydropathica, HYD; P. humicola, HUM; P. humicola x inundata, HUMxINU; P. inundata, INU; P. sp. kelmania, KEL; P. lacustris, LAC; P. megasperma species complex, MEG; P. multivora, MUL; P. nicotianae, NIC; P. occultans, OCC; P. palmivora, PAL; P. parsiana, PAR; P. pini, PIN; P. polonica X aff. "Maryland 8," POLxMAR; P. pseudocryptogea , PCY; P. pseudosyringae, PSE; P. psychrophila, PSY; P. quercetorum, QUM; P. quercina, QUE; P. ramorum, RAM; P. riparia, RIP; P. rosacearum, ROS; P. syringae, SYR; P. taxon casuarina, CAS; P. taxon juncus (sp. nov.), JUN; P. taxon mugwort (sp. nov.), MUG; P. taxon oaksoil, OAK; P. taxon raspberry, RAS; P. taxon walnut, WAL; P. thermophila, THE; P. thermophila X amnicola, THExAMN
Site ID Year(s) planted Total
samples Positive samples
% positive samples
Number Psp. Phytophthora spp.
GUAD6 2011-2012 3 3 100 13 CHL, CRA, HYD, INU, LAC, PAR, PCY, POLxMAR, ROS, CAS, OAK, THE, THExAMN
GU1A 1994-1995 7 7 100 11 ACE, ASP, CRA, KEL, LAC, MUL, PCY, PSE, ROS, OAK, WAL
UPC 2012 8 7 88 6 CAC, CRA, INU, MEG, PAL, PIN
GRCE 2013 5 4 80 5 CAC, HED, MUL, PIN, OAK
STMC 2002 10 8 80 5 CAC, MUL, PIN, PSY, QUE, OAK
ADOB5 2008 12 6 50 4 CAC, MUL, NIC, RAS
CARA 2012 11 4 36 4 CAC, EUR, MUL, PIN
JACB 2009 6 2 33 3 CAC, MUL, OCC
STSU 2012 4 2 50 3 CAC, CRA, HED
COPAR 2006-8 5 3 60 3 EUR, MUL, JUN
PAJ 2007-8 3 3 100 3 INU, RAM, RIP
TOMA 2013 9 3 33 3 MUG, QUM, ROS
CSS 2011 8 3 38 2 CAC, PCY
STRP 2002-2003 5 2 40 2 CAC, HED
ADOB 2005 17 3 18 2 CAC, CRA
PENT 2014 3 2 67 2 CRA, SYR
COYM 1998-9 3 2 67 2 HUM, HUMxINU
JACA 2009 8 1 12 1 CAC
STWA 2013 2 2 100 1 CAC
STWB 2013 3 1 33 1 CAC
STWC 2013 5 2 40 1 CAC
TAR 2008 4 1 25 1 CAC
CCR2 1980’s 3 2 67 1 MUL
CALE 2013 6 0 0 0
CCR3 1990’s 3 0 0 0
GCBH 2013 2 0 0 0
LEND1 2011 3 0 0 0
LEND2 2009 1 0 0 0
LEND3 2009 6 0 0 0
TIC 2010 4 0 0 0
TOCA 2012 8 0 0 0
P. cactorum most
common and widespread species
Phytophthora species recovered, by site
P. acerina, ACE; P. asparagi, ASP; P. cactorum, CAC, P. chlamydospora, CHL; P. crassamura, CRA; P. europaea, EUR; P. hedraiandra, HED; P. hydropathica, HYD; P. humicola, HUM; P. humicola x inundata, HUMxINU; P. inundata, INU; P. sp. kelmania, KEL; P. lacustris, LAC; P. megasperma species complex, MEG; P. multivora, MUL; P. nicotianae, NIC; P. occultans, OCC; P. palmivora, PAL; P. parsiana, PAR; P. pini, PIN; P. polonica X aff. "Maryland 8," POLxMAR; P. pseudocryptogea , PCY; P. pseudosyringae, PSE; P. psychrophila, PSY; P. quercetorum, QUM; P. quercina, QUE; P. ramorum, RAM; P. riparia, RIP; P. rosacearum, ROS; P. syringae, SYR; P. taxon casuarina, CAS; P. taxon juncus (sp. nov.), JUN; P. taxon mugwort (sp. nov.), MUG; P. taxon oaksoil, OAK; P. taxon raspberry, RAS; P. taxon walnut, WAL; P. thermophila, THE; P. thermophila X amnicola, THExAMN
Site ID Year(s) planted Total
samples Positive samples
% positive samples
Number Psp. Phytophthora spp.
GUAD6 2011-2012 3 3 100 13 CHL, CRA, HYD, INU, LAC, PAR, PCY, POLxMAR, ROS, CAS, OAK, THE, THExAMN
GU1A 1994-1995 7 7 100 11 ACE, ASP, CRA, KEL, LAC, MUL, PCY, PSE, ROS, OAK, WAL
UPC 2012 8 7 88 6 CAC, CRA, INU, MEG, PAL, PIN
GRCE 2013 5 4 80 5 CAC, HED, MUL, PIN, OAK
STMC 2002 10 8 80 5 CAC, MUL, PIN, PSY, QUE, OAK
ADOB5 2008 12 6 50 4 CAC, MUL, NIC, RAS
CARA 2012 11 4 36 4 CAC, EUR, MUL, PIN
JACB 2009 6 2 33 3 CAC, MUL, OCC
STSU 2012 4 2 50 3 CAC, CRA, HED
COPAR 2006-8 5 3 60 3 EUR, MUL, JUN
PAJ 2007-8 3 3 100 3 INU, RAM, RIP
TOMA 2013 9 3 33 3 MUG, QUM, ROS
CSS 2011 8 3 38 2 CAC, PCY
STRP 2002-2003 5 2 40 2 CAC, HED
ADOB 2005 17 3 18 2 CAC, CRA
PENT 2014 3 2 67 2 CRA, SYR
COYM 1998-9 3 2 67 2 HUM, HUMxINU
JACA 2009 8 1 12 1 CAC
STWA 2013 2 2 100 1 CAC
STWB 2013 3 1 33 1 CAC
STWC 2013 5 2 40 1 CAC
TAR 2008 4 1 25 1 CAC
CCR2 1980’s 3 2 67 1 MUL
CALE 2013 6 0 0 0
CCR3 1990’s 3 0 0 0
GCBH 2013 2 0 0 0
LEND1 2011 3 0 0 0
LEND2 2009 1 0 0 0
LEND3 2009 6 0 0 0
TIC 2010 4 0 0 0
TOCA 2012 8 0 0 0
19 species between
two sites on the Guadalupe river
Juncus sp: P. multivora, P. pini Willow sp: P. crassamura, P. pseudocryptogea, P. lacustris, P. pseudosyringae, P. rosacearum, P. taxon oaksoil
Juncus sp: P. pseudocryptogea
Toyon: P. cactorum, P. crassamura, P. hedraiandra
Mugwort: P. chlamydospora, P. crassamura, P.
hydropathica, P. inundata, P. lacustris, P. polonica X aff. "Maryland 8", P. taxon casuarina, P. thermophila X amnicola
38 Phytophthora species
All Phytophthora species # sites # Plant species Clade P. acerina 1 1 2 P. asparagi 1 1 6 P. cactorum 15 16 1 P. chlamydospora 1 1 6 P. crassamura 5 7 6 P. europaea 2 2 7 P. hedraiandra 3 2 1 P. humicola 1 1 6 P. humicola X inundata 1 1 6 P. hydropathica 1 1 9 P. inundata 3 4 6 P. lacustris 2 2 6 P. megasperma species complex 1 2 6 P. multivora 8 8 2 P. nicotianae 1 1 1 P. occultans 1 2 2 P. palmivora 1 2 4 P. parsiana 1 1 9 P. pini 4 4 2 P. polonica X aff. "Maryland 8" 1 1 9 P. pseudocryptogea 3 4 8 P. pseudosyringae 1 2 3 P. psychrophila 1 1 3 P. quercetorum 1 1 4 P. quercina 1 2 1 P. ramorum 1 1 8 P. riparia 1 1 6 P. rosacearum 3 7 6 P. syringae 1 1 8 P. sp. kelmania 1 1 8 P. taxon casuarina 1 1 6 P. taxon juncus (sp. nov.) 1 1 ? P. taxon mugwort (sp. nov.) 1 1 ? P. taxon oaksoil 4 7 6 P. taxon raspberry 1 1 6 P. taxon walnut 1 1 6 P. thermophila 1 1 6 P. thermophila X amnicola 1 1 6
28 “good” species - 6 described since 2014 - 2 described since the project started in August 5 described but provisional 3 putative hybrids 2 novel species P. cactorum, P. multivora and P. crassamura most widespread
About 1/4 of the ~150 species of Phytophthora
All subgeneric clades represented except 5 and 10
Big, lingering question: How many of our 38 species truly came from the nurseries?
Baiting a comparable amount of bulk soil from Big Sur forests resulted in 6 species (TBB, unpublished)
A combined effort over more than a decade of nursery, landscape and riparian isolations across Europe produced a list of ~60 species (Jung et al. 2014)
So many species
P. asparagi & P. crassamura from declining “maquis”
Declining native vegetation on Maddalena Archipelago (Scanu et al. 2015)
Dieback of Quercus ilex, Asparagus albus, Cistus sp., Juniperus phoenicea, J. oxycedrus, Pistacia lentiscus and Rhamnus alaternus
Several species of Phytophthora associated
P. asparagi most commonly isolated & most virulent on Juniperus seedlings
P. crassamura and P. ornamentata described as novel species
crassamura means “thick walled” (Scanu et al. 2015)
Fig 1. Symptoms of decline on Mediterranean maquis vegetation caused by Phytophthora spp.: a. Dead and dying trees of Juniperus phoeniceae with abnormal production of epicormic shoots; b. Mature tree of Juniperus oxycedrus showing severe wilting and red discoloration; c. Young tree of J. oxycedrus with red/bronze colour of foliage over the entire crown; d. Basal phloem lesion on a juniper tree extending up from below ground level; e. Collar and root rot on a young juniper tree; f. Extensive dieback and mortality of Pistacia lentiscus across site; g. Dieback and wilting of Asparagus albus.
(Scanu et al. 2015)
Phytophthora quercina Species first isolated from declining oaks in Central & Southern Europe in the 1990s
Most common Phytophthora in declining Central European oak forests, especially where trees die rapidly and in groups
Fine-root pathogen, specific to the genus Quercus, but found in nursery soil with other plant species
Aggressive on all Quercus species tested
Balci et al. found a close relative, P. sp. ohioensis from eastern US oak stands, but P. quercina has not been isolated in North America
Declining Q. robur showing different levels of crown dieback and chlorosis (specific symptom on calcaric soils due to advanced fine root destructions caused by P. citricola and P. quercina).
Aggressiveness of P. quercina to Q. robur roots in a soil infestation test after 6 months; left: control, right: infested soil.
APHIS ranked listed P. quercina as the #1 Phytophthora species of concern for introduction into the US
P. quercina isolation in Santa Clara Co.
Isolated from four Valley Oaks (Q. lobata); site planted in 2002
Initial isolation is the only documented baiting of P. quercina by pear; subsequent isolations were only successful with Q. robur and Q. ilex leaf bait
This represents the first detection of P. quercina in the US, confirmed by USDA
Ongoing work
Follow-up, including treatment of most critical areas (SCVWD & Phytosphere taking the lead)
Collaboration with “CalPhytos” working group and other researchers
Culture-independent techniques with frozen soil samples DNA has been extracted from most soil samples
Oomycete DNA can be detected w/ specific primers in all samples tested
Systematic studies of interesting strains
Two novel species of Phytophthora were isolated
P. taxon juncus
P. taxon mugwort
Neither could be unambiguously placed into a subgeneric clade, even with multiple (up to 6) loci
The nature of the project raises important questions about their status as native or exotic pathogens
Cla
de
7
Cla
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1
Sporangia of P. taxon mugwort
The big picture
Increased regulations following SOD have been largely successful for foliar Phytophthora species, less so for soil-borne species Move differently, symptoms less diagnostic Regulated differently
Well-meaning environmental regulations may have led to poor choices for restoration in regards to root-associated Phytophthora Choice of nursery-origin transplants rather
than seeds or natural regeneration Year-round irrigation of plants adapted to
Mediterranean climates Direct movement of soil for the purposes of
moving unculturable plant-mutualistic microbes
Oomycete diversity remains undersampled at many scales
Acknowledgments
Santa Clara Valley Water District & employees
Noah Luecke & Miles lab (CSUMB)
Rino Oguchi & Valerie Wuerz, UC Davis
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