Nguefack, Julienne2; Wulff, Ednar Gadelha5; Dongmo, J. Blaise Lekagne2; Fouelefack, F. Romain2; Fotio, Daniel2; Mbo, Joseph2; Torp, Jan6
1 Department of Plant and Environmental Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet2 unknown3 Department of Agriculture & Ecology, Crop Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet4 Department of Plant Biology, Faculty of Life Sciences, Københavns Universitet5 Department of Agriculture & Ecology, Crop Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet6 Department of Plant Biology, Faculty of Life Sciences, Københavns Universitet
The effects of essential oils (EO), cold water (CWE), hot water (HWE) and ethanol (ETHE) extracts of Callistemon citrinus L. and Cymbopogon citratus (DC) Stapf on the radial growth of Alternaria padwickii (Ganguly) M.B. Ellis and Bipolaris oryzae (Breda de Haan) Shoemaker, the control of brown spot disease, the tillering, the number of panicles and the yield increase in rice were evaluated under laboratory and field conditions. In vitro, the growth of both fungi was completely inhibited by the EO of C. citrinus and C. citratus at 4,520 mu g/ml and 452 mu g/ml, respectively. For solvent extracts, the ETHE of C. citrinus was the most active and inhibited 80-85 % of the fungal growth followed by the CWE of C. citratus with 77 % and 36 % diameter reduction against B. oryzae and A. padwickii, respectively at 10 000 mu g/ml. Under laboratory conditions, seed treatment with the EO of C. citrinus reduced the incidence of B. oryzae in seeds by 85-100 % compared to the non-treated controls. Similarly, the seed treatment increased the germination of an irrigated rice cultivar by 10.6 whereas the percentage of germinated seeds of upland rice was not significantly affected. The highest germination (85-94 was found in the non-treated and treated samples with a low incidence (0-4 of B. oryzae. Under field conditions, the combined use of the essential oil of C. citrinus as a seed treatment and spraying the plants with 2 % ethanol followed by 2 % (w/v) aqueous extracts of C. citrinus or C. citratus increased the emergence, tillering, panicles/plant and the grain yield by 25-55 % of the irrigated rice. In addition, the brown spot severity was reduced by 36-42 For the upland rice, the treatments led to similar results with the grain yield increase of 54-137 % and 20-80 % reduction in the brown spot severity. From our results, we concluded that the EO and solvent extracts of C. citrinus and C. citratus have potential as control agents against brown spot and other seed-borne fungal diseases in rice under both conventional and organic farming.
European Journal of Plant Pathology, 2013, Vol 137, Issue 4, p. 871-882