PHYTOPHTHORA NICOTIANAE عامل پوسيدگي ريشه ، ساقه ، پياز و غده هاي شبه ريزومي تعدادي از گياهان زينتي در ايران

ROOT, STEM, BULB AND RHIZOME-LIKE TUBER ROT OF SEVERAL ORNAMENTAL PLANTS CAUSED BY PHYTOPHTHORA NICOTIANAE IN IRAN

In recent years seeds, hulls, rhizomes and seedlings of ornamenetal plants have been imported accompanied by some important phytopathogenic agents. Phytophthora nicotianae van Breda de Hann was the causal agent of root, stem, bulb and, rhizome-like tuber rot of imported and home products of Rose, Lilium longiflorum, Dieffenbachia amonea, Peperomia obtusifolia, Alstroemeria hookeri. Mentioned above isolates of P. nicotianae were compared morphologicaly, physiologicaly, and isozymicaly. Colony morphology of the isolates on CMA was dense or loose rosette, lanose, and intermediate between rosette or stellate and lanose. Chlamidospores were formed abundantly in Peperomia and Dieffenbachia isolates, sphaerical, 27.4-34.3 µm in diameter. Sporangia were produced abundantly in liquid and solid cultures singly or in a loose sympodium on long stalk predominantly sphaerical and ovoid with a prominent papilla, 34.5-54.04 long*27.2-38.2µm wide (average), with length, breadth ration 1.24-1.43, noncaducous, Dieffenbachia isolates produced sporangia often attached to sporangiophore laterally and a few sphaerical sporangia had two papillae. Most isolates were heterothallic but Peperomia isolates produced oogonia and oospores when paired with either Al or A2 mating type of P. nicotianae. Antheridia were amphigynous and sphaerical, 13.3*11.(µm in diameter. Oogonia were smoth and sphaerical, 29.2µm in diameter. Oospores were sphaerical, aplerotic, pale yellow when matured, 23.612.m in diameter. The minimum temperature for growth was less than 10°C, the optimum was 29-33°C, most isolates except Diffenbachia ones grown well at 35°C. The electrophoretic estrase patterns for all isolates were similar using protein polyacrilamid gel electrophoresis. In pathogenicity tests all P. nicolianae isolates were founded to be pathogenic on their hosts. The isolates were reisolated from infected plants.