Phytophthora diversity in UK gardens

Geoff DentonPlant Pathologist

The Royal Horticultural Society

Detection Methods

Apple Baiting

Immunoassay

Nested PCR

Comparison of positive results from 2006 and 2007 from apple baiting, nested PCR and immunoassay

0

10

20

30

40

50

60

70

80

90

Apple baiting Nested PCR Immunoassay

Posi

tive

resu

lts (%

)

StemRootSoil

n=

145n=

413

n=

401

n=

144

n=

380

n=

320n=92

Positive results for the last 10 years from apple baiting, nested PCR and immunoassay

0

50

100

150

200

250

300

350

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Num

ber o

f Enq

uirie

s

Total testedPositive apple baiting resultsPositive nested PCR resultsPositive immunoassay results

Phytophthora species identified through sequencing ITS

0 20 40 60 80 100 120 140 160

P. tropicalis/capsiciP. syringae

P. sp.510P. ramorumP. quercinaP. primulae

P. porriP. pgchlamydo

P. niederhauseriiP. nicotianae

P. megaspermaP. inundata

P. ilicisP. ideai

P. hibernalisP. gonapodyides

P. fragariaeP. drechsleriP. cryptogea

P. citrophthoraP. citricola

P. cinnamomiP. cambivoraP. cactorum

P. alni

Occurrence of species (n=489)

P. citricolaP. cinnamomi

P. cryptogea

P. niederhauserii

P. tropicalis/capsici

P. ramorum

Phytophthora diversity

• In total 25 Phytophthora species have been recorded in UK gardens

• During 2006 and 2007 alone we recorded 87 different host genera

• Top hosts are; Taxus (19%), Rhododendron(5.6%), Rubus (4.2%) and Viburnum (4.2%)

1---Phytophthora sp.

---2P. syringae

1---P. nicotianae

---1P. megasperma

2--3P. gonapodydies

--3-P. fragariae

-227P. cryptogea

---6P. citrophthora

24920P. citricola

22-32P. cinnamomi

--1-P. cactorum

ViburnumRhododendronRubusTaxus

Following the identification of the Phytophthora species, potential new hosts for the following species have been found:

• P. cactorum: Phylliopsis• P. cambivora: Prunus laurocerasus• P. citricola: Abutilon, Aesculus, Buddleja, Ceanothus, Convolvulus,

Cornus, Enkianthus, Fothergilla, Fremontodendron, Helleborus, Lavendula, Pieris, Sorbus, Santolina, Symphoricarpus, Taxus, Trachelospermum, Wisteria

• P. citrophthora: Ceanothus, Daphne, Heuchera• P. cryptogea: Anemone, Araucaria, Calluna, Caryopteris, Choisya,

Cistus, Delphinum, Heliopsis, Heuchera, Prunus laurocerasus, Tilia, Polemonium, Ribes, Rosmarinus, Ruta, Taxus, Thuja

• P. gonapodyides: Rubus, Sorbus, Taxus• P. hibernalis: Hebe• P. megasperma: Hedera

Proportion of Pythium and Phytophthora identified by sequencing of ITS region, through

all detection methods

0

50

100

150

200

250

300

2006 2007

Year

Num

ber o

f Enq

uirie

s

Pythium

Phytophthora & Pythium

Phytophthora

61%9%30%

57%

5%

38%

Comparison of total Phytophthora and Pythium identified, by method and sample

0

50

100

150

200

250

Stem (PCR) Roots (PCR) Soil (PCR) Stem (Bait) Roots (Bait) Soil (Bait)

Num

ber o

f Enq

uirie

s

PythiumPhytophthora

Pythium species identified through sequencing ITS

0 5 10 15 20 25 30 35 40 45

Py violaePy vexans

Py vanterpooliiPy ultimum

Py sylvaticumPythium sp.Py parvum

Py oligandrumPy montanum

Py monospermumPy minus

Py macrosporumPy irregulare

Py intermediumPy helicoides

Py heterothallicumPy chamaehyphonPy attrantheridium

Occurrence of species (n=160)

Py attrantheridium

Py intermedium

Py sylvaticum

Pythium diversity

• In total 17 Pythium species have been recorded in UK gardens

• During 2006 and 2007 alone we recorded 72 different host genera

• Top hosts are; Taxus (12.6%), Prunus (4.9%), Rubus (4.2%) and Cornus (3.5%)

--47Pythium sp.

1---Py vexans

2-13Py sylvaticum

-1--Py oligandrum

---1Py montanum

---1Py monospernum

---1Py macrosporum

---1Py irregulare

-132Py intermedium

-212Py heterothallicum

2213Py attrantheridium

CornusRubusPrunusTaxus