Napier grass is a tropical perennial C4 grass with superior biomass yield and quality. It is an important forage crop and a promising feedstock for lignocellulosic biofuel production. However, precise phenotyping and genotyping data to support the molecular breeding of Napier grass are scarce. A Napier grass F1 mapping population (segregating pseudo-F 2 population) was generated by hybridizing genetically distant parents (N190 × N122) with contrasting flowering-time-and biomass-related traits.

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... rue F1 hybrids were confirmed with a simple sequence repeat marker, vegetatively propagated, and phenotyped in replicate field plots for 2 years (2 harvests per year) in Citra, FL, USA (29.40N). Near-normal distributions were observed for flowering date, plant height, number of tillers, stem diameter, and leaf width, confirming the quantitative nature of these traits. The annual dry biomass yield of F1 hybrids varied between 21.0 and 41.1 t ha −1 . The highest-yielding F1 hybrids showed remarkable hybrid vigor exceeding the annual biomass production of the highest-yielding parental accession (26.9 t ha −1 ) by 52% and the biomass yield of the control "Merkeron" cultivar (29.2 t ha −1 ) by 41% over 2 years. F1 hybrids with delayed flowering time along with significantly increased biomass yield were also identified. Late-flowering accessions allowed maximum biomass harvest before formation and dispersal of seeds, reducing invasion risk. The developed mapping population will be an excellent resource for identifying quantitative trait loci and candidate genes for flowering-and biomass-related traits in Napier grass that will accelerate the improvement of this non-domesticated bioenergy crop. K E Y W O R D S