English abstract
In March 2013, 90% of mature bean plants (Phaseolus vulgaris L. cv. Kendo) grown on a commercial farm in the north of Oman (Barka) developed symptoms of root rot and necrotic streaks on the crown area of the stem and wilted. A Pythium spp. was isolated consistently from roots and basal stems on 2.5% potato dextrose agar (PDA) and V8 (100% vegetable juice) plus 1.5% agar technical. Colonies of Pythium spp. on PDA and V8 plus agar developed abundant aerial mycelia, with the main hyphae being up to 10 μm wide. Zoosporangia were made up of terminal complexes of swollen hyphal branches of different lengths and up to 22 μm wide. Oogonia were terminal, globose, and smooth with a 26-μm diameter (average of 20). Antheridia were mostly intercalary, sometimes terminal, and broadly sac-shaped, 15 μm long and 11 μm wide (average of 20). Oospores were aplerotic, 23 μm in diameter (average of 24), with walls 1 to 2 μm thick at 25°C (ambient temperature).
