Using of RAPD-PCR for Separation of Pythium spinosum Sawada into Two Varieties: Var. spinosum and var. sporangiiferum.

Pythium spinosum var. spinosum and Pythium spinosum var. spoanriiferum, 2 varieties of Pythium spinosum were isolated from the rhizosphere soil of wheat grown in Bear-Elmansura zone (The New Valley Governorate, Egypt) and from the mud soil at the bank of Sheatan Lake (Tunisia), respectively. Cardinal temperatures, mycelial growth, zoospore production, and morphological features using light and electron microscopy under different conditions revealed that the 2 isolates studied were distinct different varieties. The randomly amplified polymorphic DNA (RAPD) banding patterns of 8 isolates of Pythium spinosum generated by 3 random oligonucleotides showed a very high level of variation, allowing these isolates to be separated into 2 groups. These results support the separation of Pythium spinosum into 2 varieties. The 2 varieties were proved to be highly pre-emergence damping-off pathogenic pythia against cucumber germinating seeds.