THE GENUS PYTHIUM - An-Najah National University

PYTHIUM DEBARYANUM auct. non Hesse, Waterhouse, Mycol. Pap. 109,
15pp. (1967) (as de Baryanum); Hesse, Inaug. Diss. Halle: 1-76(1874). Figs.
30-33
COLONY MORPHOLOGY: Colonies on CMA showing a radiate growth;
some aerial mycelium developed especially around petri dish margin.
MYCELIUM: Main hyphae 2.5-6 (av. 3.4)llm wide. SPORANGIA: Terminal or
intercalary, globose to subglobose, 15-35 (av. 24.1 ± 1,7-95% c.!.) urn diam.
Zoospores produced at 5-1S-C. OOGONIA: Mostly terminal, globose, 16-25 (av.
19.7 ± 0.8-95% c.i.) urn diam. ANTHERIDIA: 1-2(-3)foogonium, mostly
monoclinous, originating at some distance from oogonium base, never
hypogynous or sessile, occasiounally diclinous, mostly club-shaped. OOSPORES:
Aplerotic, 15-20 (av. 16.4 ± 0.4-95% c.L).um diam, wall 1-2 (av. 1.2 ± 0.195%
c.i.) urn thick, ooplast 7-11 (av. 8.9 ± 0.3 95% C.I.) .urn diam.
TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5° C, optimum
23-30oC, maximum 350C. Daily growth rate on CMA at 250C 23.8 mm.
MATERIAL EXAMINED: ex Psidium guayava L., Nablus (FCCAU
104.3);ex Prunus amygdalus (L.) Batch, Nassareyeh (FCCAU 104.4); and ex
soil, Hebron (FCCAU 104.1).
OCCURRENCE: Infrequently isolated from roots, and rarely from soil
(found in 6% of the soils sampled). This species was also isolated from diseased
roots of Cucumis sativus L. and Lycopersicon esculentum Mill in Jordan,
(Mamluk, Skaria & Abu-Blan, unpublished, in Mamluk et al., 1984; Vestal,
1954).
PYTHIUM DELIENSE Meurs, Phytopath.Z. 7:179 (1934).
OCCURRENCE: Rarely isolated from irrigated fields (in 9% of the soils
sampled); it was absent in nonirrigated fields.
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