Phytophthora and Pythium Associated with Feeder Root Rot of Citrus in the Transvaal Province of South Africa |
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| Authors: | A H Thompson A J L Phillips E Nel |
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| Institution: | Vegetable and Ornamental Plant Institute, Private Bag X293, Pretoria 0001, South Africa;Plant Protection Research Institute, Private Bag X134, Pretoria 0001, South Africa;Institute for, Soil, Climate and Water, Private Bag X79, Pretoria 0001, South Africa |
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| Abstract: | Mild to extensive feeder root rot was present in all 23 orchards, with trees showing symptoms of citrus decline from nine areas in the Transvaal Province of South Africa. Phytophthora nicotianae and Pythium spp. were isolated from diseased roots and rhizosphere soils in all areas sampled. Isolations from diseased feeder roots showed P. nicotianae present in 26% of orchards during Spring and 61% of orchards during Autumn, while Pythium spp. were present in 56% of orchards during Spring and 65% of orchards during Autumn. In isolations from baited rhizosphere soils, P. nicotianae was present in 56% of orchards during Spring and 52% of orchards during Autumn, while Pythium spp. were present in 69% of orchards during Spring and 82% of orchards during Autumn. In rhizosphere soils, the mean population density of Pythium spp. was higher than that of P. nicotianae throughout the season. Only P. nicotianae was consistently isolated during thesurvey. Different Pythium spp. were isolated of which two were tentatively identified as P. paroecandrum and Pythium‘Gp.G’. |
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