1. Advances in the
morphological and
molecular
identification of
Pythiogeton species
Z. Gloria Abad
USDA-APHIS-PPQ-PSPI,
Beltsville, MD, USA
Motoaki Tojo
Osaka Prefecture University,
Sakai, Osaka, Japan
Cytoplasm evacuation of
sporangium of Pythiogeton

2. Background and objectives
1. Pythiogeton in the Kingdom Straminipila with
it's only nine species is a not widely studied
genus.
2. In the USA, P. ramosum (Minden 1916) and P.
autosytum (Drechsler 1932) have been
reported.
3. Three putative new Pythiogeton species were
isolated from ornamental plants (cypress,
English-ivy and alyssum) which showed root rot
symptoms during the summer 2003 in NC, USA.
4. These Pythiogeton species were characterized
on morphology and the ITS rDNA sequences.

3. Kingdom: Straminipila
Phylum: Heterokonta
Class: Peronosporomycetes
Order: Pythiales
Family: Pythiaceae
Genus: Pythium
Phytophthora
Halophytophthora
Pythiogeton

4. Patterns of sporangium development in Pythiaceae
Cysts
Zoospores
Flagellum Flagellum
synthesis synthesis
& &
Vesicle Cytoplasmic Cytoplasmic
cleavage cleavage
Clear Flagellum Non or
synthesis Unclear
&
Cytoplasmic
cleavage
Sporangium
Pythium Phytophthora， Pythiogeton
Halophytophthora

5. 0:00 0:30 1:00
1:30 2:00 3:00
Zoospore
development in
Pythiogeton sp. 1
4:00 5:00 18:00
Bars = 20μm

6. 0:00 0:10 0:20
0:30 0:40 0:50
Zoospore
development in
Pythiogeton sp. 3
0:60 1:20 2:00
Bars = 20μm

7. Sporagium of
Pythiogeton sp. 1
produced in water
culture
Sporagium of Pythiogeton sp. 1 produced in radish
root hairs. No obvious symptom was observed

8. Morphology of Pythiogeton sp. 1
1 7 1-5. Sporangia
6. Appressoria
7, 8. Cytoplasm evacuation
and zoospore development
2 3 4 8 through vesicles (arrowhead)
9. Zoospore with flagella
10. Encysted and germinated
5 6 9 zoospores
11. Sporangia formed in
cypress roots after artificial
10 inoculation (arrow heads)
12. Sporangia formed around
cypress roots after artificial
11 12
inoculation
Bars: 1-10 = 20 µm
Bars: 11, 12 = 50 µm

9. Morphology of Pythiogeton sp. 2.
22 25 28 22-25. Sporangia
26. Appressoria
29
26 27, 28. Development of
zoospores out and inside
of sporangia
30
29. Empty sporangium
23 with a vesicle (arrowhead)
27 30. Encysted zoospores
31-33 Sporangia formed in
and around English Ivy
24
roots after artificial
inoculation
31 32 33
Bars: 22-30 = 20 µm
Bars: 31-33 = 50 µm

10. Morphology of Pythiogeton sp. 3
34 38 41 34-39. Sporangia
40. Appressoria
39 41. Empty sporangium
35 with vesicle (arrowhead)
42. Encysted and
germinated zoospores
36 37 40 42
31-33 Sporangia formed
in and around root of
Alyssum roots after
artificial inoculation
Bars: 34-42 = 20 µm
43 44
Bars: 43, 44 = 50 µm

11. P.arrhenomanes.39
P.volutum.64
P.vanterpoolii.61
P.periilum.54
P.graminicola.29
P.inflatum.63
P.aphanidermatum.71
P.deliense.42
P.porphyrae.06
P.destruens.74
P.insidiosum.64
P.grandisporangium.91
Pythiogeton.English.Ivy.03.287 Pythiogeton sp. 1
Pythiogeton.Cypress.02.1000
Ph.cambivora
Ph.cinnamomi
Ph.ilicis
Ph.cactorum
Ph.capsici
Halophytophthora.batemanensis -
P.viniferum.94
P.violae.63 .
P.rhizosaccharum.78
P.ramificatum.17
P.middletonii.49 Pythiogeton sp. 2
P.rostratum.56
P.longisporangium.93
P.bifurcatum.35
P.orthogonon.53
P.nunn.51
P.campanulatum.04
P.acanthophoron.52
Pythium.sp.HS.66
P.ultimum.var.sporangiiferum.6
P.splendens.42
P.glomeratum.39
P.heterothallicum.62
P.undulatum.30
Achlya.bisexualis
0.1
Phylogenetic tree based in internal transcribed spacer ribosomal DNA
region [ITS rDNA (ITS1, 5.8S, ITS2)] sequences constructed using
Neighbour-joining analysis. Achlya bisexualis was used as outgroup.

12. Summary
1. Three putative new species, Pythiogeton sp. 1,
2 and 3 were isolated from ornamental plant
roots in North Carolina, USA.
2. The all species infected to roots of their host
plants and radish, but had no visible symptom
in an inoculation test performed in Petri dish.
3. The phylogenetic tree based in ITS rDNA
shows that all Pythiogeton are a solid species
and the closest are members that belong to
Pythium (P. grandisporangium) than
Phytophthora.