A NEW RECORD OF A SPECIES OF PHYTOPHTHORA AS A CAUSAL AGENT OF PEPPER WILTING IN IRAN
AR RABIEIFAR1, A ALAVI1 and A ALIZADEH2
1Plant Pests and Diseases Research Institute, Evin, Tehran, Iran; 2Department of Plant Pathology, College of Agriculture, Tarbiat Modares University, Tehran, Iran
Background and objectives
15 species of Phytophthora have been isolated from different plants in Iran. Among them is Phytophthora capsici, the causal agent of pepper wilting . We have been attempting to detect the new causal agent of significant amounts of infection and pepper mortality in Tehran province.
Materials and methods
Infected tissue of roots and crowns of wilted pepper plants, Capsicum annuum, in Mardabad (Karaj) were washed, dried and plated on selective media containing CMA supplemented with Ampicillin (50O p.p.m.), benomyl (40 p.p.m.), rifampin (10 p.p.m.) and PCNB (20 p.p.m.), and incubated in the dark at 20°C for 3 days. Hyphal tip isolates were then selected.
Results and conclusions
Colonies were colourless, radiate on CMA and MA, but irregular and fluffy on PDA. Hyphal diameter was 2.5-7.5 with average of 4.97 mm without swelling. and the cardinal temperatures for growth on CMA were 5 (min), 25-30 (opt) and 33°C (max). Sporangia were produced in liquid media especially at 15°C after 48 h, spherical, eilipsoid, ovoid, obpyriform, papillate (1-2) occasionally after a basal swelling on sporangiophore and (22.5-62.5)x(20-45) with average of 44x31.5 mm in dimension. The average l/b ratio of sporangia was 1.38:1 with that of the papilla 3.48 mm. Sporangiophores were long and irregularely branched with diameter 2.5-3.75 and an average of 2.56 mm. Oospores were formed on carrot piece media  after incubation at 20°C for 4 months and markedly aplerotic, 20-35 with average of 26.37 mm. Oogonia were 22.5-40 with average of 32.16 mm and smooth walled. Antheridia were amphigynous, spherical or short cylindrical, (10-20)x(7.5-15) with an average of 14.15-12.38 mm in dimension. Chlamydospores were not present on any media. On the basis of morphological characteristics and the taxonomic key , Phytophthora citrophthora was identified and its pathogenicity was demonstrated on pepper plants grown in the infested soil with inoculated carrot pieces under greenhouse conditions. This is the first report of isolation and pathogenicity approval of this fungus on pepper in Iran.
1. Ershad D, 1992. Phytophthora species in Iran. Agricultural Research Organization, Tehran, pp. 217.
2. Stamps DJ, Waterhouse GM, Newhook FJ, Hall GS, 1990. Mycological Paper 162.