Energycane (Saccharum spp. X Saccharum spontaneum L.) biomass Production, Reproduction, and Weed Risk Assessment Scoring in the Humid Tropics and Subtropics

There is growing interest in biofuel production, and energycane (Saccharum spp. x S. spontaneum L.) has been proposed as an important biofuel and biomass crop. However, little is known about the growth and ecology of this new crop, especially in the tropics. The present study evaluated the performance of 14 energycane clones, elephantgrass (Penniseium purpureum Schumach.), and two sugarcane (S. officinarum L.) varieties in the humid tropics of Costa Rica, and eight energycane clones in the subtropics of Florida. In the tropics, energycane's growth and biomass production were highly variable when comparing clones. However, the best performing clones US85-1006, US88-1006, and US78-1014 produced almost twice the dry biomass (>64 Mg ha(-1)) compared with sugarcane varieties Pindar and Q-132 (21-39 Mg ha(-1)). In the subtropics, energycane fresh (52-79 Mg ha(-1)) and dry (20-30 Mg ha(-1)) weights were less than half of those in the tropics. Fnergycane clones flowered in both environments, but pollen viability was three to four times higher (>40%) in the tropics than in the subtropics, although viable seeds were found only in the tropics. Weed risk assessment (WRA) scores were higher in the tropics than in the subtropics and varied among clones. The results confirmed that energycane is a promising feedstock for biomass production and could play an important role as a biocnergy crop when grown in the tropics and subtropics, but due to genotype x environment interactions, the tradeoff between biomass production and weedy and invasive risk must be assessed for each individual clone and environment.