Abstract

Many landraces and improved cultivars of sorghum (Sorghum bicolor) grown in Uganda have late maturity and are susceptible to several biotic and abiotic stresses. Introgression of the rhizomatous trait from perennial sorghum (Sorghum halepense) could improve stress tolerance. However, phenotypic characterization of exotic perennial sorghum germplasm under Ugandan environmental conditions is essential to select desirable genotypes. Rhizome-forming capacity of 192 S. bicolor × S. halepense backcross tetraploid families developed in a temperate North American environment was evaluated at two locations in Uganda over two consecutive growing seasons. Numbers of rhizomes and emerging shoots as well as mean distances from shoot to crown were evaluated. Forty-seven percent of families were moderately to strongly rhizomatous in the first season of growth and this value rose to 91% in the second season. Developing perennial grain sorghum for East Africa will require hybridization between exotic perennial and locally adapted germplasm. Screening for emerging rhizome-derived shoots in early generations is simple, rapid, and effective; however, more detailed selection based on both aboveground and belowground rhizome traits is recommended for later generations. Researchers and farmers should work together to find suitable ways in which perennial sorghum might fit into new types of crop and livestock systems.

Key words: Rhizome, perennial sorghum, rhizome buds, ramets.