1. Stramenopila
Distinguishing Characteristics
Cell Walls have Cellulose (-1,4 glucose linkage) vs. glucans.
Lysine biosynthesis is DAP (like plants), vs. AAA like true fungi
Heterokont- biflagellate-- anterior tinsel and whiplash flagella (vs. lateral whiplash).
Aquatic and soil fungi.

2. Stramenopila Other Characteristics
Motile spores formed in a sporangium
Sexual reproduction by gametangial contact
Diploid through most of the life cycle
Somatic structures are unicellular and holocarpic, or rhizoidal, or coenocytic.

3. The Hyphochitryomycota
Anterior tinsel flagellum
Aquatic habitat
Some parasites (on algae and fungi), others saprobes
Thallus is holocarpic or eucarpic
Holocarpic species are endobiotic
Eucarpic species may be mono- or polycentric
Zoosporangia are inoperculate, zoospore release is through a discharge tube

4. Eg. Rhizidiomyces apophysatus

5. The Oomycota
Zoospore biflagellate, heterokont—posterior facing whiplash, anterior facing tinsel (emerge adjacent)
Sexual Reproduction by gametangial contact
Oogamous—two different types of gametangia, contact, contents of one flow into the other
Oospore is the sexual spore--thick walled resting spore
Meiosis occurs in gametangium
Haplobiontic (only diploid thallus, no haploid thallus)
Some are holocarpic, no mycelium
Some are eucarpic, but monocentric with rhizoids
Some produce extensive mycelia with coenocytic hyphae

6. Oomycota (5 orders, 65 genera, 500-800 species)—two we will discuss:
Peronosporales
Saprolegniales

7. Saprolegniales long terminal sporangia with more than one egg per oogonium
“Water molds” occur abundantly in clean water. Mostly saprobes but a few parasites (Saprolegnia parasitica) causes diseases of fish and fish eggs.
Most are hermaphroditic and homothallic (self-fertile).
May be mono- or dimorphic (two spore forms)

8. Eg. Saprolegnia

9. Sexual Reproduction in the Oomycota

10. Eg. #2 Achlya bisexualis Very similar asexual phase
Unique sexual phase
Studied by John Raper in the 40’s and 50’s demonstrating a complex hormone system involved in sexual development
Hormone Source Function
A Female somatic thallus Induces antheridial branches
B Male thallus w anther init. Induces formation of oogonial initials
C Oogonial initials Attracts anther branches
D Antheridia Oogonium & oospere differentiation

11. Achlya

12. Peronsporales oval-lemon shaped zoosporangia with one oosphere per oogonium
Well developed coenocytic mycelium
Most advanced and specialized order of the Oomycota
All members are monomorphic (one type of zoospore)
Three Families- distinguished by the structures that bear sporangia

13. Families in the Peronosporaceae
Pythiaceae- sporangia directly borne on vegetative hyphae. These fungi are saprophytes or facultative parasites (very destructive)
Peronsoporaceae- sporangia borne on branched, determinate sporangiophores (protrude through stomates). Obligate parasites called the “Downy Mildews”
Albuginaceae- chains of sporangia on club shaped sporangiophores that rupture host epidermis to form a white crust on leaf surface. Obligate parasites called “White Rusts”.

14. Ex. Pythium Debaryanum

15. Pythium Asexual Zoosporangia

16. Pythium Sexual Reproduction

17. Pythium Oospores

18. ‘Damping Off’ (Pythium)

19. Phytophthora

20. Phytophthora- a devastating facultative parasite

22. Zoospore Release in Phytophthora sojae

23. Peronosporaceae- the ‘Downy Mildews’
Obligate parasites
Branched, determinate sporangiophores
Sporangiophores protrude through host stomates

24. Ex. Plasmopora viticola (Peronosporaceae)

25. Downy Mildew on Grape

26. Albuginaceae- the ‘White Rusts’
Obligate parasites
Club shaped sporangiophores (inside host leaf)
Sporangia rupture leaf epidermis and appear as a white crust

27. Ex. Albugo cadida (Albuginaceae)