DEVEL LOPMEN OF RA NT APID DIAG GNOSTIC METHO FOR C OD Xanth homonas campestris pv. sesam AND SC c s mi CREENIN OF NG SESAMUM GERM S MPLASM F FOR RES SISTANCE E

Abstract

Sesame (Sesamum indicum L.) locally called as Til is an important conventional and industrial oil seed crop in Pakistan and is mainly cultivated on marginal lands in the rain feed and irrigated areas throughout the country. Pakistan ranks fourteenth among major sesame producing countries in the world. Pakistan is facing a chronic shortage in edible oil and the situation is getting serious with alarmingly explosions of population. Its indigenous production is below the utilization level and there exists wide gap between production and utilization. However, its production is declining due to prevalence of several biotic and abiotic factors. Among the biotic factors, bacterial blight incited by Xanthomonas campestris (pamel) Dowson sesami (Sabet and Dowson, 1960) Dye (Xcs) is most serious and devastating disease and responsible for colossal losses and frequently complete failure of crop. The appears on young as well as adult plants, and produce extensive blight on the foliage, stem and petioles, resulting in defoliation collapse of tissue and sterility of flowers. The pathogen is responsible for sesame production constraints during monsoon season. Despite the shortage of edible oil, no profound efforts have been made on this important oil seed crop with reference to diseases. At present, the disease has become a limiting factor and a serious impediment to successful production of sesame in Pakistan. To handle the shortage of edible oil, there was an urgent need to explore the basic information on host pathogen interaction. The present work consisted of four experiments. The first study was the monitoring of the disease. The disease had been established in some fields of Punjab xix province from the past 25 years where repeated outbreaks of the disease were being observed during monsoon season each year. Most of the farmers were not certain about bacterial blight symptomology and its casual organism. Most of the commercial varieties used by farmers were imported whose disease resistant information was not known. Bacterial blight was found in areas where diverse soil, pH, temperature, relative humidity and rainfall. The severity of the disease depends on the amount of the rainfall. The sowing dates had a significant influence on the % incidence of the bacterial blight of sesame. The incidence of the disease decreases with delay of sowing dates. The second study was conducted to the pathogen was isolated from different parts of the infected plants including stem, twigs and seeds using different media as nutrient agar, yeast dextrose agar, yeast dextrose calcium carbonate agar and colonial behavior of the isolates were recorded by exposing these at different temperatures, hypersensitive responses and pathogenicity were also performed. It was also recorded that an approximate temperature of 28oC with relative humidity 85-95 % and rainfall enhance the pathogenic infestation. The third study was production of polyclonal antibodies. The polyclonal antibody was produced in a rabbit. It was tested against homologous antigen (host antigen) etc., ELISA kit was developed which could be used for large scale screening of germplasm. The forth study was conducted large scale screening of sesame genotypes identified resistant resources to be utilized by the breeder in the evaluation of disease resistant varieties leading to increase in production and substantial benefits to the farmers. It is hoped that present studies will provide basis for improved prediction and diagnosis together with formulation of management strategies preferably breeding for long lasting resistance against this disease.