THE GENUS PYTHIUM - An-Najah National University

PYTHIUM DIMORPHUM Hendrix & Campbell, Mycologia 63:979 (1971).
OCCURENCE: This species was isolated only once from a soil in Tulkarem.
PYTHIUM DISSIMILE Vaartaja, Mycologia 57:421 (1965). Figs 36-41
COLONY MORPHOLOGY: Colonies on CMA forming a radiate growth
pattern; no development of aerial mycelium. MYCELIUM: Main hyphae 2.5-6
(av. 3).Almwide. SPORANGIA: Terminal or intercalary,consisting of complexes
of toruloid outgrowths of hyphae. Zoospores readilly produced at 1O-20oC.
OOGONIA:Terminal, occasionaly intercalary, globose, smooth 10-15 (av. 12.4
± 0.4-95% c.1.).Alm diam. ANTHERIDlA:Mostly lacking, rarely hypogynous,
monoclinous or diclinous. OOSPORES: Plerotic, wall 1-1.5 (av. 1.0 ± 0.4-95%
c.I.)..um thick. Ooplast 5-8 (av. 6.3)..um diam. TEMPERATURE-GROWTH
e
RELA TIONSHIPS: Minimum ro-c, optimum 20-25°C, maximum 30C. Daily
o
growth rate on CMA at 25C 6.4mm.
MATERIAL EXAMINED: ex Viciafabae L., Jenin (FCCAU 106.6); ex soil,
Gaza (FCCAU 106.1), Nablus (FCCAU 106.2), and several other isolates. .
OCCURRENCE: infrequently isolated from diseased roots, and also rarely
from irrigated soils (found in 14% of these soils); it was absent in nonirrigated
soils. Only a few records are known for this species. It has been recorded from
soil and Pinus radiata in Australia (Vaartaja, 1965), from soil in the Netherlands
(Plaats - Niterink, 1975), from agricultural soils in Germany (in Plaats-
Niterink, 1981), from cultivated soils in England (Ali, 1982) and the West Bank
of Jordan (AIi, 1985)
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