Seasonal variation in population levels of Pythium species in irrigated and non-irrigated fields in the West Bank of Jordan and the Gaza Strip

Abstract

Seasonal fluctuations in soil populations of Pythium spp. were studied from 27 irrigated and non-irrigated fields subject to different cropping practices in the West Bank and the Gaza Strip over a period of 13-29 months. Pythium populations showed significant seasonal variations in 14 of these fields. Generally, soil population levels were highest in the cooler seasons and lowest during midsummer. Individual taxa such as Pythium ultimum, P. oligandrum and P. group ‘HS’ followed the general seasonal pattern of total Pythium. P. aphanidermatum in irrigated fields followed a different seasonal pattern; it tended to peak in summer when soil temperatures were relatively high. The influences of biotic, chemical and physical environmental factors and cropping practices on the pattern of seasonal fluctuations of Pythium spp. populations are discussed.