THE GENUS PYTHIUM - An-Najah National University

IV. DESCRIPTIONS OF SPECIES
Whenever possible two to three isolates of each Pythium species have been
deposited in the Fungus Culture Collection of An-Najah University (F C C A
U). The following scale is used to describe the degree of presence of Pythium
species in soil: constantly present, found in 80-100% of soils; mostly present,
found in 60-80% of soils; often present, found in 40-60% of soils; seldom
present, found in 20-40% of soils; and rare, found in 1-20% of soils.
PYTHIUM ACANTHICUM Drechsler, J. Wash. Acad. Sci. 20:408 (1930) Figs
2-7
COLONY MORPHOLOGY: Colonies on CMA showing a distinct rosette
pattern; no aerial mycelium. MYCELIUM: Main hyphae 2.5-5 (av.3.2).um wide.
SPORANGIA: often intercalary, occasionally terminal; subglobose 15-28 (av.
20.6± 2.1-95% C. Ij um diam, often forming complexes of irregular subglobose
elements attached together by filamentous portions. Zoospores produced in
water culture at room temperature. OOGONIA:Mostly terminal,occasionally
intercalary, globose 14.0-24.0 (av. 20.6 ± 0.6-95% C.I) .urn in diam; wall
echinulate, spines conical with blunt tips, 1-6 (av. 3.5).um long. ANTHERIDIA:
1(-2)joogonium, mostly monoclinous arising at distance upt to 25)lm below
oogonium base, rarely diclinous, often possessing branched vegetative
prolongations; antheridial cells often inflated with few constrictions applied to
the oogonium with narrow or broad contact interph ase. OOSPORES: plerotic,
17-21 (av.19.4 ± 0.5-95% C.I).um diam, wall 1.5 ± 0.12 95% C.I.um thick,
coplast 9-13 (av. 10) .urn diam. TEMPERATURE-GROWTH
RELATIONSHIPS: Minimum 10 0 C ,optimum25-30 0 C, maximum 37 0 C, Daily
growth rate on CMA at 25 0 C 9mm.
MATERIAL EXAMINED: ex soil, Tulkarm (FCCAU IOU); ex soil, Gaza
(FCCAU 101.2) ex Malus sylvestris (L.) Mill, Nablus (FCCAU 101.6), and
several other isolates.
OCCURRENCE: Infrequently isolated from diseased roots, stream water, and
stream bed.
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