Sorghum (Sorghum bicolor (L.) Moench) is a food security crop in sub-Saharan Africa, which requires constant breeding in response to changes in the fragility of agricultural production environments. Hence, understanding and tenacious use of genetic variation in sorghum germplasm is essential for improving the crop to cope with environmental changes. The objective of this study was to determine the levels of diversity and spatial distribution of sorghum on farmers' fields in major sorghum

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... regions in Uganda. A survey involving 180 fields was conducted in three districts, namely Agago and Apac (northern) and Serere (eastern) all in Uganda. Diversity was measured in terms of number of accessions per field, the Shannon-Weaver and Simpson diversity indices. In order to assess spatial distribution of sorghum diversity on the fields, correlation analysis was carried out between diversity and geographical distances between fields. Overall, Agago district had the highest number of accessions per unit area (4.47); while Apac had the lowest (1.62). The spatial distribution of sorghum diversity showed a positive correlation (r = 0.381 for Agago, 0.124 for Apac and 0.081 for Serere), between geographical distances and diversity across the three districts; implying that fields close together share similar sorghum varieties. This can be due to sharing seeds between farmers within a given location. Sorghum diversity was spatially distributed in the fields, with fields close to each other shared most sorghum types. The levels of sorghum diversity on fields were highest in Agago and lowest in Apac district. The existing on-farm sorghum diversity offers the opportunity for improving sorghum through natural breeding against biotic and abiotic stresses.