PHYTOPHTHORA-CITROPHTHORA AND P-NICOTIANAE IN 2 CONTRASTING CITRUS PLANTATIONS IN THE WEST-BANK, MIDDLE-EAST

During a survey extending over 8 months, Phytophthora strains were iso lated from two Citrus plantations in the West Bank contrasting in agri cultural management and climate (Jordan Valley and Tulkarem regions). This was the first survey for Phytophthora on Citrus in this region. F our techniques were used for isolations (soil dilution, direct isolati on from plant material, and baiting soil with Citrus leaf discs or lup in radicles). Species were identified using morphological and growth c haracteristics. Only two species were detected, namely Phytophthora ci trophthora and P. nicotianae. Highest numbers of P. citrophthora and P . nicotianae isolates were obtained by soil dilution and Citrus baitin g, with the former discriminating in favour of P. nicotianae. Direct i solation from plant material and lupin baiting were the least successf ul recovery methods. Differences in spatial distribution of isolates c ould be related to differing agricultural management and geographical features of the plantations. Although the species distribution was sim ilar in the two plantations, the total number of isolates recovered di ffered significantly between subsites in the Jordan Valley plantation. The number of isolates obtained from sequential soil samples also var ied and was generally higher in samples taken in the cooler, wetter wi nter months. Significantly more isolates were found in the Tulkarem pl antation. Irrigation at Tulkarem was by flooding, while spot irrigatio n was used in the Jordan Valley. The longer established Tulkarem plant ation contained a mixture of Citrus cultivars unlike the newer Jordan Valley orchard.