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INTEGRATING HOST RESISTANCE WITH CULTURAL PRACTICES TO MANAGE ASCOCHYTA BLIGHT OF CHICKPEA
INTEGRATING HOST RESISTANCE WITH CULTURAL PRACTICES TO MANAGE ASCOCHYTA BLIGHT OF CHICKPEA C. AKEM and S. AHMED Germplasm Program, International Center for Agricultural Research in the Dry Areas (ICARDA), P.O. Box 5466, Aleppo, Syria. Background and objectives Ascochyta blight of chickpea, caused by Ascochyta rabiei is the most damaging disease of chickpea worldwide. It is especially severe on winter-sown chickpea when conditions favouring crop growth also favour the development of the disease. The disease is favoured by cool and wet weather and attacks chickpea at any growth stage. Infected plants often develop elongated and sunken dark lesions on leaves, stems, pods and seeds [ 1]. These lesions girdle stems, weaken branches and kill entire plants. Severe early infections can result in total crop failure. The use of resistant cultivars represents the most effective, economical and enviromnentally sound means of controlling ascochyta blight. Some resistant chickpea cultivars have been developed at ICARDA [2] and released to farmers in the Mediterranean region, but the existence of pathotypes of A. rabiei renders the resistance in these cultivars unstable and limits their effective life under production. In order to prolong the durability of the resistance in these cultivars, an integration of host resistance with other control options is necessary. Other options for control of the disease are the use of fungicides as minimal foliar sprays when epidemics are iminent, and the modification of agronoiffic or cultural practices to create micro-cliinates unsuitable for rapid disease initiation and spread. Fungicide use has limited scope in the region because the effective chemicals are costly, usually unavailable and raise enviromnental concerns. The only practical alternative therefore, is the integration of host resistance with cultural practices. Materials and Methods Multi-locational experiments were initiated during the 1996/97 cropping season in northern Syria to evaluate different cultural practices in conjunction with host resistance for managing ascochyta blight on winter-sown chickpea. Treatments included four planting dates, four row spacings and seed treatments with different fungicides integrated with host resistance. Four chickpea lines, comprising one resistant, two moderately resistant and one susceptible selection, were used in all the trials. The experimental designs were split-split plots with lines as main plots, seed treatments as sub-plots and different cultural practices as sub-sub-plots. All trials were replicated three times. Infected debris collected from previous seasons were spread within plots to increase inoculum potential in the plots. Ascochyta blight severity and grain yield data were recorded. Results and conclusions First year field results from these trials showed that seed treatments with the fungicide Thiabendazole (Tecto) at the rate of 3 g per kg, significantly reduced initial disease severity by up to 40% on all the lines tested, compared with the un-treated controls. Delayed planting within the winter months of November to February, resulted in lower disease severity and increased grain yield of up to 20% in the moderately resistant chickpea lines. Wider row spacings also resulted in lower disease severity and increased grain yield in the susceptible and moderately resistant lines due to the added effect of increased branching. These fmdings suggest that it is possible to grow chickpea with moderate levels of resistance to ascochyta blight during winter, by integrating host resistance with some cultural practices. This would reduce the disease pressure and help to prolong the productive life of the cultivars grown under highly variable pathogen populations during the winter months. References 1. Nene, Y.L., Reddy, M.V., Haware, M.P., Ghanekar, A.M. and Anun, K.S. 1991. ICRISAT Information Bulletin no. 28; 52 pp. 2. Singh, K.B and Reddy, M.V. 1996. Theoretical and Applied Genetics 92:509-515,