Context. Panicum coloratum is a relatively undomesticated small-seeded warm-season forage grass. Seed shattering, an extended reproductive period and non-synchronic seed maturation limit harvested seed yields. Low seed quantity and quality hinder pasture establishment and discourage its use.

Aims. To assess whether seed yield potential could be improved by breeding, we sought to measure variability in traits related to seed production including phenotypic plasticity in response to environmental cues, and estimated narrow-sense heritability, prospective genetic gain after selection and co-heritabilities in seed yield components.

Methods. Seed retention (SR), number of panicles (PN), seed number per panicle (SN) and seed weight (SW) were measured in plants growing in the field. Clonal replicates of 13 genotypes were assessed in 2007 and 2010 and half-sib families derived from these genotypes were measured in 2010.

Key results. Phenotypic variability among genotypes was related to genetic factors for all measured variables. Two broad groups of accessions showing differences in SR were studied. Phenotypic plasticity in SR differed among genotypes and was negatively related to levels of SR, implying that stable high-SR genotypes could be selected in a breeding program. Maximum narrow-sense heritabilities were 0.89 and 0.41 for SN and SR, respectively, with estimated gains after selection around 30%. The best results were achieved if selecting for SR at 3–5 weeks after anthesis. Low genetic correlations and extremely low co-heritabilities between other characters and seed yield components discourage the possibility of indirect selection.

Conclusion. Moderate increases in seed production potential may be achieved after selection for SN, SW and SR in P. coloratum var. makarikariense.

Implications. Improvements in SR and other seed yield components would facilitate harvest, increase yield and consequently increase profitability to growers and stimulate pasture adoption by farmers.