A study of quality of sesame seeds produced in Uganda

A study on quality of sesame seeds produced in Uganda was done. The objectives of the study were to determine the health status and quality of sesame seeds produced in Uganda;evaluate locally available materials in Uganda for use as substrates in germination test and examine selected seed-dressing chemicals for control of seed-borne fungal pathogens of sesame. A total of 30 seed samples were collected form Northen, North-eastern, North-Werstern, Eastern and Central regions of Uganda. The samples were harvested during the 2000/2001 crop season. Afterwards, the seed samples were taken to the Danish Government Institute of Seed Pathology for Developing Countries (DGISP), Denmark, where screening for quality was done. Purity analysis, germination and seed health tests substrate was carried out using New Vision (Uganda) newspaper as the local material. Sorting of seed by salt solution and seed treatment using Dithane M-45 were evaluated for reducing seed-borne pathogens of sesame. The inert matter found in seeds was mainly grass and soil particles. Seed purity was performed with the objective of determining the percentage composition by weight of the samples tested and the identity of the various species od seeds and inert particles, which constituted the samples. The results showed that sesame seeds produced in Uganda are of high purity since 97% of the samples collected had 98% purity, the minimum recommended by the Uganda Seed Company (USC). The germination percentage was generally low, since only 46% of the samples assayed had 75% germination, the minimum recommended by the Uganda Seed Company. Most of the abnormal seedlings were a result of primary infection by fungal pathogens. The New Vision newspaper was not a suitable germination substrate since it caused negative geotropism of the roots. Sorting of seeds by salt solution was also ineffective. The sunken seeds thought to be healthy had many infected seeds and abnormal seedlings. Similarly, the floated seeds thought to be diseases had many healthy seeds and normal seedlings. Seed health test results revealed presence of 12 fungal species on seeds (Cercospora sesame and Alternaria sesamicola were the most abundant). However, control of these seed-borne pathogens by Dithane M-45 was effective. There was almost complete eradication of seed-borne pathogens. Out of 12 fungal species, it was only A. sesamicola which persisted in a few samples but its range of infection was greatly reduced form 0 - 66% to 0 - 0.5%. Generally, the quality of sesame seeds produced in Uganda was found to be low. This was largely due to seed-borne pathogens. Consequently, it is proposed that planting seed be seed-dressed with Dithane M-45 to minimize seed-borne infection so as to ensure production of better quality seeds. Since seed quality can be expressed in terms of purity, health, viability and vigour, production of pathogen-free seeds will meet one of the vital quality standard requirements.