Study on the Bacterial Leaf Spot Disease of Sesame

Abstract

Seedling infection of sesame (Sesamum orientale L.) was produced following seed or soil inoculation with X sesami Sabet and Dowson causing the bacterial leaf spot disease (Marad Ed-Dam). The symptoms which differed from that caused by Pseudomonas sesami Malkoff in Texas was described in detail. Seedling infection was produced by a concentrating of 103 - 104 cells/ml. added to soil or seeds but was most severe at 108-109 cells/ml. It occurred at 20-35°c soil temperature, 20-40 per cent soil moisture and 70-85 per cent relative humidity but the optima were 20-26°c, 30-40 per cent and 75-85 percent respectively. Applications of nitrogen increased the resistance of seedlings to infection but at higher levels (36-54 kg. N/feddan) germination and seedling growth were retarded. A number of sesame varieties responded similary to seedling infection, leaf infection and natural field infection and hence the seedling infection technique was proposed as a precise method of assessing the resistance of sesame varieties to the bacterial leaf spot disease. It has the advantage of assessing large number of varieties within a short period under uniform conditions. X sesami survived in soil for 5-7 months on seed for up to 16 months and in infected trash for 8-18 months and this indicated the possibility of its survival between the cropping seasons of sesame to initiate primary infections. The pathogen could be eradicated from seeds by chemical fungicides and bactericides such as Abavit B, Fertix 6704 and Formalin and these were recommended for use in the control of the sesame disease after further trials in the Field