Production of conidia by Peronosclerospora sorghi on sorghum crops in Zimbabwe |
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| Authors: | C H Bock M J Jeger L K Mughogho E Mtisi & K F Cardwell |
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| Institution: | ;Natural Resources Institute, Central Avenue, Chatham Maritime, Chatham, Kent ME4 4TB, England, UK,;Department of Phytopathology, Agricultural University of Wageningen, P.O.B. 8025, 6700 EE, Wageningen, The Netherlands,;Southern African Development Co-operation/International Crops Research Institute for the Semi-Arid Tropics/Sorghum and Millet Improvement Program, PO Box 776, Bulawayo,;Plant Protection Research Institute, Department of Research and Special Services, PO Box 8100, Causeway, Harare, Zimbabwe,;International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria |
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| Abstract: | Factors affecting the production of conidia of Peronosclerospora sorghi , causing sorghum downy mildew (SDM), were investigated during 1993 and 1994 in Zimbabwe. In the field conidia were detected on nights when the minimum temperature was in the range 10–19°C. On 73% of nights when conidia were detected rain had fallen within the previous 72 h and on 64% of nights wind speed was < 2.0 m s?1. The time period over which conidia were detected was 2–9 h. Using incubated leaf material, conidia were produced in the temperature range 10–26°C. Local lesions and systemically infected leaf material produced 2.4–5.7 × 103 conidia per cm2. Under controlled conditions conidia were released from conidiophores for 2.5 h after maturation and were shown to be well adapted to wind dispersal, having a settling velocity of 1.5 × 10?4 m s?1. Conditions that are suitable for conidia production occur in Zimbabwe and other semi-arid regions of southern Africa during the cropping season. |
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